[Android] Add keystore and manifest test cases for packaging tool.

1. Create test_data directory for hosting test target file, such as:
   manifest, keystore etc.
2. Add keystore and manifest test cases for packaging tool.

BUG=https://github.com/crosswalk-project/crosswalk/issues/779
Merge pull request #781 from junmin-zhu/testcase

[Android] Add keystore and manifest test cases for packaging tool.