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
diff --git a/java/resources.go b/java/resources.go
index 7aa909e..f9d7a05 100644
--- a/java/resources.go
+++ b/java/resources.go
@@ -47,7 +47,7 @@
 			continue
 		}
 		resourceDir := filepath.Join(common.ModuleSrcDir(ctx), resourceDir)
-		dirs := common.Glob(ctx, resourceDir, nil)
+		dirs := ctx.Glob(resourceDir, nil)
 		for _, dir := range dirs {
 			fileListFile := filepath.Join(common.ModuleOutDir(ctx), "res", dir, "resources.list")
 			depFile := fileListFile + ".d"