Make minor code/algorithm tweaks, fix bugs.

base.py
- In calc_dwells2.calc_cooldown_times(), switch to default numpy.interp() behavior for values outside the 'x' range instead of specifying NaN. The use of NaN's caused these values not to be included in cooldown time estimates, when in fact they should be included.
- Update logger info to be more useful.
- Change variable names to be more descriptive and/or less confusing.
- Add bogus data option so that some structured data is returned by calc_dwells2(). This helps prevent further post processing and plotting from choking on cases where the supplied configuration does not limit dwell time in the given max dwell time. This results in this data not being plotted (due to the use of numpy.nan types), rather than errors being raised.

pyger.py
- In calc_constraints2(), add a check to see if n_ccd is included in the constraint object before accessing it. In cases were pyger is run solely for models that do not use ccd count, this fix prevents an error from being thrown.
- In calc_dwell2_stats(), remove filtering out of NaN types since this is no longer necessary.