Rename input actions by editing its item in the list

Closes #3682 (closed)

Input action items became editable after 908f75c. This caused the confusion you see in the above issue.

To solve this, I removed the old rename dialog and the rename button. Now actions are renamed by editing the item in the tree.

Input preset items are not editable. This could be confusing for some users (as discussed with @akien-mga on irc). A solution could be to make them editable, but show an error message after confirming the edition (e.x.: "Input presets cannot be renamed").