Resource shared libraries: fix theme references

Theme values that would reference other theme values would not work
if they were declared in a shared library.

We now introduce a parallel resource type to TYPE_DYNAMIC_REFERENCE,
TYPE_DYNAMIC_ATTRIBUTE, which allows us to lookup and resolve
theme value references from shared libraries.

Bug:28687378
Change-Id: I4f2364e3e8b567679f90784fcaaea12b6b05e926