Add some utils function for text management for query.
Add helper import on __init__ of mdrender.
Increment djmail version to 0.6
Minor fix on project creation.
Cosmetic fixes on references services and user form.
History: improvements on history app

- Handle deleted objects.
- Add project to freezers.
- Make values implementation optional.
- Split choices to separated module.
- Add own mixin.
History: add tests.
Notifications: new notification application.
Notifications: move all notificatications related emails to notifcations app.
Notifications: add test for notifications app.
Notifications & History: modify all related models and resources for work with new api.
Remove old notification mixin.