Added option to selectively save files.

Added extra settings options and a save menu item.
Choose files to be saved using checkboxes in settings menu.
Save using File-->Save-->Selected menu.
Replaced array lookup with function

Replaced the "colourmap.py" method with a colour map function. Generates
the RGB values for the JET colour map, used formulas from
http://www.metastine.com/?p=7

Should be the same colours but look slightly different. Also starts from
blue, rather than black.
Tidied up the code and removed redundant code

Removed code that doesn't seem to do anything as the ReDraw() function
is called at the end which does the same job.

Removed commented debug statements.
Edited colour map function and max_value slider

Added an if statement to make the new colour map more like the old one.

Changed how the max value from slider gets set and used. Seems to make
more sense (to me anyway) , and gets called less often.
Removed references to old colourmap.py and colormap.h

Removed references to the colourmap.py in the code and deleted the files
Removed Iminv.pro from tracking in repo an added a .gitignore file

This is a configuration file for each PC. Shouldn't really be in this
repo. The .gitignore should stop us commiting our configurations by mistake.
Got colourMap() working

Problem with the calculation giving numbers greater than 255, this was
being modulo(255) by the qRgb function to produce numbers that were too
small.

Put in a couple of if statements to catch the max value. Seems to
produce a colourmap that is same as before
Fixed problem with inverted image rendering

Problem was when image is inverted it produces floats not ints. Changed
reDraw() function to cast to floats. Means ints get a decimal point and
zero, but floats are unchanged.
Fixed memory leak

There was a major memory leak in pbinversion.cpp file, polar_b(...)
routine, which is fixed now.
Other small changes do not affect functionality.
Forgot to remove debugging code
Saving flags and unresponsive GUI

1. Saving flags are now all linked to a single menu option in
Options->Settings->Multiple files. They also used for
File->Save->Selected ! even so it is a bit misleading.
2. Operations->Invert a set should not freeze the GUI now but update the
progress bar.