treemanifest: remove treemanifest._intersectfiles() In preparation for the optimization in the following commit, this commit removes treemanifest.matches()'s call to _intersectfiles(), and removes _intersectfiles() itself since it's unused at this point.

manifest: add some tests for manifest.matches() There were no tests for the various code paths in manifestdict.matches(), so I added some. This also adds a more complex testing manifest so that any bugs relating to traversal of directories are more likely to be caught.