Favourites Directories

Support for custom favourites shortcuts.

Issues and thoughts:

- default_value for 'favourite_directories' doesnt seem to work, engine validation return str and not list
- dont know how this setup will do on a non-multiroot system
- cant get the default value for the icon to work, doesnt seem to pick up the value
- possibly need some special cases if people want to use versions etc. that arent part of the app initialization
- refine paths in tk-multi-workfiles:
	- support the templates to have optional fields, that can be populated when the data is present. which could be the versions etc.