Batcave

- Added
- Added pkgtype arg to build.MavenBuilder class.
- Added ant support.
- Added support for creating, switching and merging git branches.

- Changed
- Pass release argument to maven in build.MavenBuilder.
- Moved argument processing from build execution to Product instantiation.
- Converted initializers to use tuple() instead of None guard.
- Accept default args in ActionCommandRunner.
- Improved git branch management.
- Upgraded google-cloud to 0.33.1.
- Upgraded GitPython to 2.1.10.
- Upgraded setuptools to 39.2.0.
- Upgraded unittest-xml-reporting to 2.2.0.

- Changed
- Upgraded docker to 3.3.0.
- Upgraded setuptools to 39.1.0.

- Removed
- Removed sysutil.recopytree().

- Changed
- Remove Google Cloud login on every command.

- Changed
- Need to login to Google Cloud instance before every command.

- Added
- Added lang.flatten() and flatten_output argument to sysutil.syscmd().

- Changed
- GitPython doesn't handle pathlib.Path objects.

- Changed
- Fixed issue where fileutil.unpack does not work if dest argument is used.