Add a 'removeunusedresources' script that goes through an app and removes

Add a 'removeunusedresources' script that goes through an app and removes
all the unused resources. It uses the 'findunusedresources' script to find
the resources, and the 'xmlstarlet' command to edit xml files. The
result is an uncommitted git change that you can verify, modify if
needed, and then check in.
Also put some more fixes in the findunusedresources script to keep
it from reporting false positives.