gitignore : update to match all the new execs
Core: Move parts of IPMatching into CC file

This moves a minor amount of the source code out of the header but it
also helps me debug the problem with MESSENGER.
Core: Have IntegralAutoGainDetector reuse parts on IntgralDetector

Importantly this fixes the extrema test for IP in Ames Stereo
Pipeline. We weren't doing a test around the whole circle. Instead we
were accidently doing something like a C shape. This meant that before
we were detecting a lot of IP in a chain. That made their descriptors
non unique. Surprisingly our filtering could work through all that.

This fixes the case were MESSENGER data wasn't working correctly. This
should also greatly increase the amount of detected IP for all other
cases.