SaveFig plot naming scheme and auto_increment

[Areustle]

When plots are generated they always save the file as the default matplotlib savefig name "Figure_1.png" or something like that.

Proposal:

• Provide a way to customize name prefix for saves plot images.
• Set a default name. Probably default to the simulation output file name like nuspacesim_run_<timestamp>_<number>.png
• Auto increment : 1, 2, ...

[Areustle]

Attention of @jfkrizmanic and @smayotte, any thoughts?

[smayotte]

I think this is really important. On the default filename maybe it would make more sense to have the default name of a plot be the name of the respective plotting function? nuspacesim_run_<timestamp>_<number>.png would make it a bit difficult to quickly distinguish plots. If we go with something like <plot_function_name>_<timestamp>.png that would make it a lot clearer (albeit maybe not as straightforward in implementation)

[Areustle]

I think that's a good point @smayotte . How about a scheme like <simulation_name>_<plot_function_name>.png where simulation_name is the same as the user defined output FITS file name with its existing default value.

[smayotte]

I spent some time working on this and have a working implementations for both the --plotconfig and --plot options. I hope the implementation is not too clunky. Should I commit that to a branch again so that you can review it?

[Areustle]

Yes you should commit it to a branch and open a pull request. Reference this issue by including the string "#20" in the PR text and we'll start a code review.