Reorganize greta processing tools, Improve G_LIMMON parsing capability

Remove greta parsing tools from gretafun.py and place in separate file.
Add function to parse G_LIMMON.dec comments.
Add function to parse G_LIMMON.dec output.
Add import statement to gretafun.py to load parsing functions into gretafun.py namespace.
Make DateTime import consistent with usage elsewhere.
Remove extraneous spacing.
Modify code to keep all lines under 80 characters.

Signed-off-by: Matthew Dahmer <matthew.dahmer@gmail.com>