added read sol_mpa functionality

Implemented read of solar magnetic probe array data.

* Implented 'sol_mpa' as a diagnostic.
* Created a separate avg function so that mpa data can be read.

Complications:
* MPA data actually records 2^14 data points instead of 2^13.
* MPA data is a vector quantity AND the diagnostic has 4
  probes associated with it.

* Minor fixes:
* Fixed some obsolete comments.

Future thoughts:
* Need to implement a scalar vs vector diagnostic plotting.
* Continue to keep changes from the analysis side hidden from the
  plotting side.
implemented scalar vs vector for vme_avg functions
polished off plotting of sol_mpa
changed convention for diag_constructor
combine both basic_2d_plots into generic 2d_plot_scalar
accidentally found & fixed wrong color on raw plot bug
modified subplot behavior and added notes.txt
added subplot functionality to my plotting routines
plot vector now calls on plot scalar for each component
simplified vme_plot_diagnostics
plot sol_mpa across multiple shots
cleaned up obsolete code