Add class constants as namespace variables

The class constants in TutorialApplication are now global constants
in the ConeMaker namespace.
Create an interface base class for Tool
Port the cursor to a Tool
Make DemoApp use our new Tool
Make DemoApp restore previous config if possible
Remove ConeMaker class

DemoApp will most probably morph into it at some point.
Update .pro file to compile all the new stuff
Remove the giant ogre head from scene
Create ObjectInserter

It'll hoepfully insert ogres.
Make DemoApp handle multiple tools
Expose cursorNode from TileCursor
Make ogre tool actually insert ogres

And by ogre tool, I of course mean 'ObjectInserter'.
Create ToolBox

This is a meta-tool that will relay signals only to the 'active'
tool.
Create a Nothing tool

This will be the default active in the toolbox.
Fix crash when switching tools