Matrix advanced features and Generic python installing instructions

[sonntagsgesicht]

added some convenience for the Matrix module:

• draw letters, numbers and icons
• flit and invert the display
• use different formats to set the full display pixels

and some lines to install and use the library with a generic python installation (no Raspberry Pi required).

[Gadgetoid]

Awesome stuff, thank you- I'll dig up my Flotilla kit and see if I can get this tested/merged!

[Gadgetoid]

I had to make a couple of fixes for Python2/Python3 cross-compatibility, but nothing major.

[sonntagsgesicht]

A pleasure. Thanks for considering my contributions.