Various improvements to Canvas examples

Various improvements to Canvas examples

I noticed these examples were rather "aestetically
challenged" and decided to make it a test case for our
WIP style guidelines.

- Use consistent margins (12 px)
- Use proposed color palettes
- Use proposed fonts and header styles

I created a new Slider graphic and moved this into
the shared folder as I think it is useful for other examples.

I removed a lot of unused files which seem to have been added
but never actually used.

I also found several bugs in our implementation, including
not scaling or rotation around the correct origin.

In many cases I simplified the examples, removing
variables/sliders where they did not add significantly
to the example itself.

Change-Id: Ie09da33deaf56a3ec45a2031b87a24a8602e994a
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>