Add --non-constant-id to aapt.

This option enbables creating resource constant in the R class
that are not actual constant, but simply static fields.

The goal is to build library projects with these types of
IDs so that the constant does not get inlined in the library
code, since the ID for the library resources only are not
the final values.

The final resource IDs, generated from the main project and
its library(ies), will have proper constant with the final
values.

This allows us to generate binary library bundle (a jar file
and associated resources) that can be distributed. Additionally,
this will let us make the library project support in Eclipse
much more robust and a better user experience overall.

Change-Id: Ibe2f08d68493fde658fc3f7606abf7446f312ad2