ZEPPELIN-3374. Improvement on PySparkInterpreter
A few improvements on PySparkInterpreter.
1. Refactor PySparkInterpreter to make it more readable
2. Code completion features is totally broken, fix it in this PR
3. Reuse the same test case of IPySparkInterpreter.
[Bug Fix | Improvement | Refactor
Repository: zeppelin
Updated Branches:
refs/heads/master 8238b711c -> aefc7ea39
ZEPPELIN-3374. Improvement on PySparkInterpreter
### What is this PR for?
A few improvements on PySparkInterpreter.
1. Refactor PySparkInterpreter to make it more readable
2. Code completion features is totally bro