Auto publish experiment

Does not currently work. Works if the item is saved in content editor, but does not work if the item was updated by unicorn (suspect eventdisabler is to blame)

May need to manually manipulate publish queue, or add the items to publish as fake dependencies of the root item being published instead of queuing them.
Merge branch 'master' into publishing-experiment

Conflicts:
	src/Unicorn/Properties/AssemblyInfo.cs
	src/Unicorn/Serialization.config
Add unicornSyncBegin, unicornSyncComplete, and unicornSyncEnd pipelines to enable hooks for stuff like auto publish
Efficient auto-publishing using a custom publish queue