Initial commit containing the initial code

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Created the Layer class and its subclasses

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Added constructors to the Layer* classes

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Changed the tools, SchetsControl and Schets to use layers
* Schets is now layer-based
* The tools add layers to Schets instead of drawing directly on a bitmap
* An unnecessary method was removed from SchetsControl
* The Schets object in SchetsControl is now accessable via a property

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>