Revert "Remove edit mode button from total weight limit panel"

This reverts commit 981756e80b5d0009bf3aa96974ca20befa03bede.
Remove tool selection from total weight limit edit box
Correctly switch classes in edit mode button when resetting edit mode
Implement backend functionality to update TWL value

TWL is short for Total Weight Limit
Add input for editing total weight limit
Show confirmation dialog when toggling read-only mode if total weight limit has been edited
Update total weight limit in model when new value is input
Send updated total weight limit to backend
Define unit of measure in total weight limit in edit and read-only mode
Merge pull request #352 from finnishtransportagency/edit_total_weight_limits

Edit total weight limits