[PROJECT.py] sorts targets and toolchains for help option

Sorts targets and toolchains for help option and adds new option -L to
generate the list with possible projects to generate.
[PROJECT.py] adds cmdline option to use program_name instread of program_id
[PROJECT.py] add option 'clean'

Adds the cmdline option clean (to clean the export folder) and some
minor things (spelling and option order).
[PROJECT.py] removed the sys.exit() after cleaning
Merge pull request #563 from ohagendorf/cmdlineoptions4project

[PROJECT.py] some additions and minor changes to cmdline options