Change style of __init__ file (#7)
Add a default .plot() method to all SysTest objects.

The SysTest base class now includes a plot() method that takes the results of a SysTest and passes them through (if they're plottable) or returns an object with a .savefig() method that doesn't do anything (if they're not) so we never have to do checks in the main program for whether the results are plottable. (#7).
Update default plot() method for SysTests (#7)
Add better weight computation to hsc/base_tasks.py (#7)
Change "field" terminology (for a sum of CCDs) to "visit". (#7)
Add bright star cutoff to Task config (#7)

Plus some various config-related tweaks.