Add command line interface to allow scripts to be run from sasview.exe

[pkienzle]

Allow scripts from the command line:

sasview -m module [args...]
    Run module as main.
sasview -c "python statements"
    Execute python statements with sasview libraries available.
sasview -i 
    Start ipython interpreter.
sasview script [args...]
    Run script with sasview libraries available
sasview
    Start sasview gui

Partially addresses #2237

[pkienzle]

We could also add a --jupyter command line option which opens up a server on localhost with everything setup. It'll increase the size of our installed package though, especially if we include jupyterhub with a nodejs distribution.

[pkienzle]

I don't have a windows box handy so couldn't test the installed package on windows.

Do we need multiprocessing freeze support?

I don't know how modern qt apps handle console vs. gui support. Maybe need to do something like creating a separate sasviewcom.exe for the console.

[pkienzle]

Oops... accidentally did "git commit -a" and this includes fixes for #2228 which I didn't clear out first. Also I noticed that we no longer have a compiled module so I tweaked the doc build a bit, and perhaps broke it. I'll look into separating these to different PRs.

[pkienzle]

Replaced with #2280.