Updated local copy of Rivets

Soon to move to a build tool and remove local copies from the repo...
After logging in return to previous URL instead of 'exec'
Factored out syncing model results from the API into a mixin
Refactored minions model to use withCachedSync() mixin
Updated x-minion-list template for adjusted model syntax
Moved x-tag mixins into the elements folder
Updated paths for x-tag mixins move
Removed unused datamodel mixin
Add fallback for peculiar race-condition when using dataset
Minor syntax cleanup
Moved setting the cache into the mixin