* Change OAL generator tool to runtime.

Step 1. change project structure. API links and maven pom.

* Part of metrics class generation

* Metrcis class generated.

* Set up the basic structure of new OAL engine.

* Finish metrics generation.

* Support dispatcher generation.

* Format codes.

* Generate dispatcher all methods.

* Implement disable in hardcode.

* Clear up

* Fix compile startup.

* Update license and document of new OAL engine.

* Fix rat.

* Disable class output in default

* Copy from @kezhenxu94 's test PR, https://github.com/apache/skywalking/pull/3110

* Wait for the mount command to finish

* New stream annotation.
- Inventory annotation example:
@Stream(name = ServiceInventory.INDEX_NAME, scopeId = DefaultScopeDefine.SERVICE_INVENTORY, storage = @storage(builder = ServiceInventory.Builder.class, deleteHistory = false), kind = StreamKind.Inventory)

- Metrics annotation example:
@Stream(name = ServiceRelationClientSideMetrics.INDEX_NAME, scopeId = DefaultScopeDefine.SERVICE_RELATION, storage = @storage(builder = ServiceRelationClientSideMetrics.Builder.class), kind = StreamKind.Metrics)

- Record annotation example:
@Stream(name = SegmentRecord.INDEX_NAME, scopeId = DefaultScopeDefine.SEGMENT, storage = @storage(builder = SegmentRecord.Builder.class), kind = StreamKind.Record)

- TopN annotation example:
@Stream(name = TopNDatabaseStatement.INDEX_NAME, scopeId = DefaultScopeDefine.DATABASE_SLOW_STATEMENT, storage = @storage(builder = TopNDatabaseStatement.Builder.class), kind = StreamKind.TopN)

* no message

* Stream annotation finish.

* Make stream processors to be the singleton class.

* Fixed the compile errors.

* Modify the OAL module for this annotation refactor.

* Add apache license header.

* Duplicate import.

* Fixed check style error.

* Rename metric to metrics.

* Fixed test case execute failure issues.

* Move oal tool back into main repo, and fix compile issue.

* Fix two bugs.

* Remove all generated codes.

* Make all oal generated codes out of source control.

* Make mvn compile and package work.

* Fix test cases.

* Make compile right and provide new documents.

* Remove an unnecessary tokens file.

* Add source attr into StorageEntity, and remove the this attr from InventoryType.

* Make RegisterLockInstaller works based on InventoryProcess registered info.

* 1. Fixed the bug of the cluster node sync failure cause by curator instance cache is null.
2. Fixed the bug of the collection in remote data builder is not initialized.

* 1. Re-generate indicator.

* Fixed the bug of the collection in remote data builder is not initialized.

* Fixed the bug of the remote client created but not  initialize.

* Support metrics downsampling.

* Fixed a check style error.

* Support new indicator core.

* Block 2 unaccessible methods.

* Add service call as manual indicator and refactor the core DIspatcherManager