General cleanup and preparation for fitting

Added a function to core.py that returns a prior func
for a model (based on a number of parameters).

Also turned random comments into docstrings

Used np and plt instead of from pylab import *

And other miscellaneous changes
Comments for the core.py component wrapper funcs
More docs and fixes to core.py
Changed capitalization of report.py methods to Python style
New system for setting parameters to estimate

Along with a number of other changes:
- Builder now includes an array, estimate_params, in which the
  parameters to estimate are set.
- In addition, there are arrays for parameter means and variances
  for each of the parameters to estimate. These are used to calculate
  the prior.
- The plotting routines in nbd_mcmc_c3 have been broken out into their
  own function, generate_figures, and all figures are included in the
  report, along with the Python code.