Support for storing OAT files in app directory

Changes to installd:
- dexopt now allows oat_dir param for custom output directory
- Added helper method calculate_oat_file_path for calculating oat file
  output location based on oat_dir and apk_path.

Bug: 19550105
Change-Id: I6b079207310583adeb6dad918a58034a059e34c4