Add globbing to filesystem mocking

Add globbing to filesystem mocking so that more code can be tested
against the mock.  Also moves the filesystem mock to pathtools,
and renames pathtools.GlobWithExcludes to pathtools.Glob, replacing
the existing pathtools.Glob.

Test: blueprint tests
Change-Id: I722df8121bc870c4a861d7c249245c57dcb607be