Make Rewrite layer pluggable

[sumashivaprasad]

Initial review draft. Adding Tests for new code are still pending. Am working on them Existing tests are passing.

[sumashivaprasad]

Fixed all Test Case failures in grill-driver-cube and added UTs. Test cases failing due to Rewriter not getting inited in QueryExecutionService. Looking into it

[sumashivaprasad]

Fixed grill server UT failures.

Grill-cli - one test is failing still . Looking into it

Failed tests:
TestGrillQueryCommands.testQueryCommands:82->testExecuteSyncQuery:224 Query failed with errorCode:126 with errorMessage: Error while processing statement: FAILED: Execution Error, return code 126 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask cause:Stage-1(MAPRED): has failed! expected [true] but found [false]

Tests run: 12, Failures: 1, Errors: 0, Skipped: 0

[sumashivaprasad]

The above Issues were due to JAVA_HOME not being set. All tests are passing in grill-cli as well

Results :

Tests run: 12, Failures: 0, Errors: 0, Skipped: 0

[ghost]

Rename to Lens

[ghost]

Some basic observations -

1. Change grill to lens in all places including comments
2. All grill.* config has to be changed to lens.* config
3. Add all new config in *default.xml and regenerate apt files by running TestGenerateConfigDoc, then add it in the PR

[ghost]

if this is a constant pls make is private static final and all caps

[ghost]

The header license template has changed, please use the latest license template.

[ghost]

Does this class have to be a singleton? I think this can be contained in LensServices instance.

[sharadag]

lens code should be agnostic to DSL and specific command types. lets relook this.
we should be able to dynamically add a specific command handler in configs.