Not flattening the end-points in the averaged AIF case.
Static population AIF.
Some debugging code in place.

Need to resample high resolution AIF, need to have a commit to which I can
return to if necessary.
High resolution AIF code appears to be working.  Pixels not so dark.
Still not getting good fits though.
Population bolus arrival time set to 10% of the way into the time range.
Merge branch 'anycurve'