In client deploy mode, the driver is launched from within `SparkSubmit`'s JVM. This means by the time we parse Spark configs from `spark-defaults.conf`, it is already too late to control certain properties of the driver's JVM. We currently ignore these configs in client mode altogether.
```
spark.driver.memory
spark.driver.extraJavaOptions
spark.driver.extraClassPath
spark.driver.extraLibraryPath
```
This PR handles these properties before launching the driver JVM. It achieves this by spawning a separate JVM that runs a new class called `SparkSubmitDriverBootstrapper`, which spawns `SparkSubmit` as a sub-process with the appropriate classpath, library paths, java opts and memory.

Author: Andrew Or <andrewor14@gmail.com>

Closes #1845 from andrewor14/handle-configs-bash and squashes the following commits:

bed4bdf [Andrew Or] Change a few comments / messages (minor)
24dba60 [Andrew Or] Merge branch 'master' of github.com:apache/spark into handle-configs-bash
08fd788 [Andrew Or] Warn against external usages of SparkSubmitDriverBootstrapper
ff34728 [Andrew Or] Minor comments
51aeb01 [Andrew Or] Filter out JVM memory in Scala rather than Bash (minor)
9a778f6 [Andrew Or] Fix PySpark: actually kill driver on termination
d0f20db [Andrew Or] Don't pass empty library paths, classpath, java opts etc.
a78cb26 [Andrew Or] Revert a few changes in utils.sh (minor)
9ba37e2 [Andrew Or] Don't barf when the properties file does not exist
8867a09 [Andrew Or] A few more naming things (minor)
19464ad [Andrew Or] SPARK_SUBMIT_JAVA_OPTS -> SPARK_SUBMIT_OPTS
d6488f9 [Andrew Or] Merge branch 'master' of github.com:apache/spark into handle-configs-bash
1ea6bbe [Andrew Or] SparkClassLauncher -> SparkSubmitDriverBootstrapper
a91ea19 [Andrew Or] Fix precedence of library paths, classpath, java opts and memory
158f813 [Andrew Or] Remove "client mode" boolean argument
c84f5c8 [Andrew Or] Remove debug print statement (minor)
b71f52b [Andrew Or] Revert a few more changes (minor)
7d94a8d [Andrew Or] Merge branch 'master' of github.com:apache/spark into handle-configs-bash
3a8235d [Andrew Or] Only parse the properties file if special configs exist
c37e08d [Andrew Or] Revert a few more changes
a396eda [Andrew Or] Nullify my own hard work to simplify bash
0effa1e [Andrew Or] Add code in Scala that handles special configs
c886568 [Andrew Or] Fix lines too long + a few comments / style (minor)
7a4190a [Andrew Or] Merge branch 'master' of github.com:apache/spark into handle-configs-bash
7396be2 [Andrew Or] Explicitly comment that multi-line properties are not supported
fa11ef8 [Andrew Or] Parse the properties file only if the special configs exist
371cac4 [Andrew Or] Add function prefix (minor)
be99eb3 [Andrew Or] Fix tests to not include multi-line configs
bd0d468 [Andrew Or] Simplify parsing config file by ignoring multi-line arguments
56ac247 [Andrew Or] Use eval and set to simplify splitting
8d4614c [Andrew Or] Merge branch 'master' of github.com:apache/spark into handle-configs-bash
aeb79c7 [Andrew Or] Merge branch 'master' of github.com:apache/spark into handle-configs-bash
2732ac0 [Andrew Or] Integrate BASH tests into dev/run-tests + log error properly
8d26a5c [Andrew Or] Add tests for bash/utils.sh
4ae24c3 [Andrew Or] Fix bug: escape properly in quote_java_property
b3c4cd5 [Andrew Or] Fix bug: count the number of quotes instead of detecting presence
c2273fc [Andrew Or] Fix typo (minor)
e793e5f [Andrew Or] Handle multi-line arguments
5d8f8c4 [Andrew Or] Merge branch 'master' of github.com:apache/spark into submit-driver-extra
c7b9926 [Andrew Or] Minor changes to spark-defaults.conf.template
a992ae2 [Andrew Or] Escape spark.*.extraJavaOptions correctly
aabfc7e [Andrew Or] escape -> split (minor)
45a1eb9 [Andrew Or] Fix bug: escape escaped backslashes and quotes properly...
1cdc6b1 [Andrew Or] Fix bug: escape escaped double quotes properly
c854859 [Andrew Or] Add small comment
c13a2cb [Andrew Or] Merge branch 'master' of github.com:apache/spark into submit-driver-extra
8e552b7 [Andrew Or] Include an example of spark.*.extraJavaOptions
de765c9 [Andrew Or] Print spark-class command properly
a4df3c4 [Andrew Or] Move parsing and escaping logic to utils.sh
dec2343 [Andrew Or] Only export variables if they exist
fa2136e [Andrew Or] Escape Java options + parse java properties files properly
ef12f74 [Andrew Or] Minor formatting
4ec22a1 [Andrew Or] Merge branch 'master' of github.com:apache/spark into submit-driver-extra
e5cfb46 [Andrew Or] Collapse duplicate code + fix potential whitespace issues
4edcaa8 [Andrew Or] Redirect stdout to stderr for python
130f295 [Andrew Or] Handle spark.driver.memory too
98dd8e3 [Andrew Or] Add warning if properties file does not exist
8843562 [Andrew Or] Fix compilation issues...
75ee6b4 [Andrew Or] Remove accidentally added file
63ed2e9 [Andrew Or] Merge branch 'master' of github.com:apache/spark into submit-driver-extra
0025474 [Andrew Or] Revert SparkSubmit handling of --driver-* options for only cluster mode
a2ab1b0 [Andrew Or] Parse spark.driver.extra* in bash
250cb95 [Andrew Or] Do not ignore spark.driver.extra* for client mode