MicroPython: Blend modes and sprite/blit HFLIP/VFLIP flags

[Gadgetoid]

Add all of the SDK blend modes into MicroPython: COPY, ALPHA, MASK, PEN, DARKEN, LIGHTEN, ADD, SUBTRACT, MULTIPLY, DISSOLVE

Add HFLIP and VFLIP flags to sprite and blit.

To flip a sprite you need to specify all eight arguments, eg:

sprite(0, 0, 0, 1, 1, 8, 8, HFLIP | VFLIP)

The above blits a single sprite, 0, in the top-left corner.