SunPy reading TRACE JP2 files

This pull requests allows SunPy to turn TRACE JP2 files into SunPy maps. The main change is sunpy/cm/color_tables.py. I extracted a dictionary creation function used by all the color table definitions into a separate function. Edits to sunpy/map/mapbase and sunpy/io/jp2 were caused by the simple debugging style I was using. There are no changes to any functional code whatsoever in those files. All other file changes are required in order to enable SunPy to support TRACE JP2 files. TRACE JP2 files will soon appear on helioviewer.org.

TRACE data is stored in a more complex format than 1 FITS file = 1 image, and so is not addressed in this pull request.