IDE-1599 Integrate tern.java framework
- moved javascript related features to jsdt module
- added initial support for tern.java nature adapter
IDE-1599 fixed jsdt module build
Remove velocity repository from build
IDE-1557 refactored codes about descriptor helpers

- move classes of descriptors to com.liferay.ide.project.core.descriptor
- make class LiferayDescriptorHelper abstract
- new way to invoke descriptors' operations