ClearFont option in gfx_2d_print

[max9901]

add a way to clear a custom font.

//to reset the font.
Graphics2DPrint::clearfont();

This is my first "larger" github project and i will use this fairly simple issue as a way to see if i get the gist of the workflow.

[uvwxy]

I re-opened this ticket. I will close it once it has been merged into the source code. Please create a pull request against lib-opensmartwatch

[max9901]

I decided to leave it out because u can just use

Graphics2DPrint::setFont(NULL).

Which is not as user-friendly for a beginning Arduino user but I thought that's probably not our target audience anyway with the lib?

[max9901]

Which btw doesn't guarantee that the cursor is put in the right place I think, but we can probably merge things like this into a rewrite of the Graphics2DPrint class anyway?

[uvwxy]

Ok, we can add this with #15