Clean up abilitylibrary.js generation...

...by creating a fake module that exports the library, and also
having it require the testbattle instead of every test library.
RATIONALE: we won't always want to include all the libraries (and
they may not even all live in the same place) so we should trust
the loaded battle about which ones to import, and the simplest
way to do that is to just browserify the whole thing.

This whole thing is still terrible. At least the client doesn't
have to care about the terrible bits?