It's mostly werking nao!

Matched output with Python output up to second iteration's covariance
and means, which basically tests everything but output.

Possible bug discovered in Python version. Will have to test later.
Release 0.1

Matches Python output (minus the last band for chisqr) and works
at a decent speed.
Now converges to a correct answer independently

The program now converges to the correct answer as gives by the
original original Python program (no nodata correction in the
provisional means library), though it converges via a different
path.

Moved a lot of code to its own utility function, including file
writing, weights calculation, and other stuff.
Moved image matching to geo_utils

GdalFileIO check is now a wrapper to geo_utils::ImageInfo::compatible()