Improve compile/install as SWMF component

[drsteve]

Currently installing as part of the SWMF requires making a number of changes manually that should be automated, or otherwise handled:

• Commenting out PLE_OBJECTS in ModRamRun.f90
• Commenting out the DoUsePlane_SCB IF block in src/Makefile
• Removing the share directory
• Manually changing paths in both Makefile.conf and Makefile.def

Using with SWMF should be easier out-of-the-box and minimizing the amount of manual editing is highly desirable.

[Pheosics]

Actually, with the creation of the srcExternal directory and moving the iri and msis stuff needed for the plasmasphere stuff, the only manual change needed should be the removing of the share directory.

I have no idea why I thought manually changing the Makefile.conf and Makefile.def was necessary at the time (probably because I didn't fully understand the Config.pl), but it is definitely not needed, you can specify the options to pass to the RAM Config.pl like so

./Config.pl -o=IM:gsl=/turquoise/usr/projects/carrington,ncdf=/usr/projects/hpcsoft/toss3/grizzly/netcdf/4.4.0_gcc-6.4.0_openmpi-2.1.2