Implement "move packages into extras"

Instead of removing packages from makefiles,
move them into extras folder in the ota(zip) file.

By default, build/tools/releasetools/extras.txt is used.
If you want to customise it, define this in your BoardConfig:

TARGET_OTA_EXTRAS_FILE := device/VENDORNAME/DEVICENAME/extras.txt

Change-Id: Ic671f06237ac387083ae2a065404558312789481
Ref: https://github.com/androidarmv6/android_build/commit/103b9a57ccf9527c2044290eac6f7fc58348a76c
Call CM's minimal bootanimation

saves around ~1MB

Change-Id: Idc0167e82030db77286aad8e374c6ac824012187
small cleanup

Change-Id: I2ae2fe3a44dbd629bcd1083b77b919a2b0023d93