Choose color of calendar's tag. Fix #110.

Add choose calendar color feature, through tag :
- Add tag docType, with name and color fields.
- Default color stays colorHash one.
- Add color picker in calendar dropdown to choose the color of the tag used as calendar.

Fix bug in list_view, first or last elems year was modified.
I needed CRUD, and I looked in events file to take inspiration.
It works, but I confess I don't know what the purpose of the two erros messages (one for devloppers, the other for humans ?)