Show all creation modes in toolbar; move AI to dock

[akx]

This PR:

• cleans up the actions container (which is gently refactored in #1480) to not contain lists of actions anymore, but just actions
• fixes the toolbar to have more semantic ordering
• adds all of the creation modes to the toolbar
• ... and since the AI bits wouldn't neatly fit in the toolbar anymore, they're now moved to the dock.

This PR includes #1482.

Screenshot