Removed defunct method.
Removed defunct method and changed ordering of methods.
Modified the code layout slightly.
Changed the way some dependencies are injected.
PlacementRestriction now DI'ed.
Added tests for RoomTool.
Added tests for PlacementRestriction.
Fixed an error in some tests that were causing failures.
Added tests for additional branches.
Upon reflection, I believe the CellTool to have been a pointless abstraction that made the code needlessly complex.  All of the functionality that would have been in that tool has been moved BACK into the humble CellPanel where it belongs.  I was a little overzealous about having no logic in the GUI classes.  There is still no BUSINESS logic in them.  The most complex check that takes place now is a check for nulls.
Moved the creation of the Tools up a level to MainUI.  The tools are now passed into the LevelToolbar by dependency injection.
Knock-on changes resulting from the removal of the CellTool class.
Tests updated to work with latest code revisions.