Slight changes in Makefile

- generate CUSTOM_TARGET_PACKAGE: this makes the rom name to appear and the zip not being copied to the root directory
- remove custom cache image generation: no needed anymore
- generate zip's md5

Change-Id: Ib055309ae70dc5e8e7b217463bbb880569ff1650
Merge remote-tracking branch 'PA-build/kitkat' into kitkat