Colour scaling without lookup

Hi,

Got bored and didn't want to write my thesis so I re-did this bit of ImInv.

I've replaced the lookup table with a function called "colourMap". I've also removed any of the references to the old colormap array. I think I got all of the unused variables that were left but I'm not sure. I've also removed the assocated files from the repository too (colourmap.py etc).

I changed slightly how the slider works rather than changing the intensity, it lowers the max value that is eventually passed to the colourMap function. It just seemed a bit tidier. It's also only called once at the beginning of the draw rather than for every pixel.

I've also removed the .pro file from the repository. This is a configuration file for Qt and is specific to each computer, I now mine is different to yours, and different to Mikes. I've also added a .gitignore file so that it's not accidentally re-added.