[SPARK-15996][R] Fix R examples by removing deprecated functions

## What changes were proposed in this pull request?

Currently, R examples(`dataframe.R` and `data-manipulation.R`) fail like the following. We had better update them before releasing 2.0 RC. This PR updates them to use up-to-date APIs.

```bash
$ bin/spark-submit examples/src/main/r/dataframe.R
...
Warning message:
'createDataFrame(sqlContext...)' is deprecated.
Use 'createDataFrame(data, schema = NULL, samplingRatio = 1.0)' instead.
See help("Deprecated")
...
Warning message:
'read.json(sqlContext...)' is deprecated.
Use 'read.json(path)' instead.
See help("Deprecated")
...
Error: could not find function "registerTempTable"
Execution halted
```

## How was this patch tested?

Manual.
```
curl -LO http://s3-us-west-2.amazonaws.com/sparkr-data/flights.csv
bin/spark-submit examples/src/main/r/dataframe.R
bin/spark-submit examples/src/main/r/data-manipulation.R flights.csv
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #13714 from dongjoon-hyun/SPARK-15996.