Add the ability to cancel an ISO repository synchronization.
Mention sync cancellation in the release notes.
Merge branch 'master' into rbarlow-iso-sync-cancellation

Conflicts:
	pulp_rpm/src/pulp_rpm/plugins/importers/iso_importer/sync.py
Use three periods when telling users we are downloading.
Merge pull request #196 from pulp/rbarlow-iso-sync-cancellation

Rbarlow iso sync cancellation