Allow common.Glob to be called by singletons

Make common.Glob take an interface that is the intersection of
blueprint.ModuleContext and blueprint.SingletonContext used by
Glob and GlobRule, allowing it to be called on either.  Also
move ExpandSources and Glob into AndroidModuleContext.

Change-Id: I8d1a3160c5dd201033afdb37210e82d8065b137d
7 files changed