Author: Michael Armbrust <michael@databricks.com>

Closes #4684 from marmbrus/explainAnalysis and squashes the following commits:

afbaa19 [Michael Armbrust] fix python
d93278c [Michael Armbrust] fix hive
e5fa0a4 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into explainAnalysis
52119f2 [Michael Armbrust] more tests
82a5431 [Michael Armbrust] fix tests
25753d2 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into explainAnalysis
aee1e6a [Michael Armbrust] fix hive
b23a844 [Michael Armbrust] newline
de8dc51 [Michael Armbrust] more comments
acf620a [Michael Armbrust] [SPARK-5873][SQL] Show partially analyzed plans in query execution