[Android] Add features class and unit test
[Android] Decouple push registration from custom API calls
[Android] Add feature usage for custom APIs
[Android] Add feature usage for table objects
[Android] Simplify feature telemetry for table calls
[Android] Add feature usage for offline (sync) tables
[Android] Add feature usage for opportunistic concurrency
[Android] Updated E2E test to ignore features header
Merge pull request #349 from carlosfigueira/androidFeatures

Android SDK features telemetry
[Android] Updated third-party legal notice
[Android] Update javadoc
[Android] Fix #351 - prevent request header list from being changed
Merge pull request #352 from carlosfigueira/android

[Android] Fix #351 - prevent request header list from being changed
Merge branch 'android' of https://github.com/Azure/azure-mobile-services into android