Support to build static Java library with Android resource

Bug: 5714516

The rationale behind this change:
- the library is compiled into a jar file, but its R class is generated
  making the constant not constant (static, not final static) (aapt
  option --non-constant-id). Also the jar file does not contain the R
  class.
- this allows the integer value to not be inlined in the compiled
  class files. Note that this prevents using switch statements.
- the main project use this jar file as a normal static library: it will
  add all the class files except the R.class.
- the main project uses the library res folder as a resource
  folder with lower priority than the main project (basically the
  main project is an overlay. This is accomplished using aapt's
  --auto-add-overlay to handle resources only in the main project
  (which the normal overlay mechanism doesn't allow).
- the main project creates R classes in the main project's
  package but also in the library's package. This is done with
  aapt's --extra-packages which accept as many packages as
  needed, separated by a :.
- manifest merging is not done yet, so
  activities/services/permissions/etc... have to be manually declared in
  the main app.

To use a static library with Android resource in your app,
1. Add the library's resource dir to your app as an overlay:
LOCAL_RESOURCE_DIR := <app_resource_dir> <static_library_resource_dirs>
2. Set the proper aapt flags:
LOCAL_AAPT_FLAGS := <apps_own_flags> --auto-add-overlay \
  --extra-packages <lib1_package_name>:<lib2_package_name>:...

Change-Id: Ifb4d2300b952ea4aaee74da1bb0c6c72ea0698a3