* ultrastardx-beta: init at 1.3.5
* libbass, libbass_fx: init at 24
* ultrastar-creator: init at 2017-04-12
* buildSupport/plugins.nix: add diffPlugins
Helper function to compare expected plugin lists to the found plugins.
* ultrastar-manager: init at 2017-05-24
The plugins are built in their own derivations, speeding up (re-)compilation.
The `diffPlugins` function from `beets` is reused to test for changes in the
plugin list on updates.
* beets: switch to diffPlugins
The function is basically just extracted for better reusability.
