(CDAP-559) Remove usage of CombinedClassLoader in ProgramClassLoader

- Also code cleanup around FilterClassLoader and ApiResourceListHolder
- Remove unneeded classes from MR and Spark job to make job starts faster.
- disable chatty logging from beanutils during test
Merge pull request #590 from caskdata/feature/fix-classloader-leak

(CDAP-559) Remove usage of CombinedClassLoader in ProgramClassLoader