added Invert Color option to Grid module

there is now a button for inverting the color pot selection to invert
with one button click, like you get in the Grasdient module
updated Description

updated the XML description to include the Invert Button inside the
Grid module and changed the Size to Resolution in the Noise module to
fit to the rest of the modules
Merge pull request #2 from inferno-op/master

added Invert Color option to Grid module