Clarify comments on alt, az, and airmass keywords.
Eliminate unused imports.
Initial commit of image software classes
Rename method of ImageSoftware
Eliminate detailed_history option in patch_headers

The only history that makes any sense is a detailed history, so that is now the only option.
Add option to save patched files to a different directory
Test patch_headers writing to new directory
Add flags to control behavior of patch_headers
Remove add_overscan, functionality now done in patch_headers

This also updates the test for adding overscan.
Trim length of FITS comments to avoid truncation.
Code to purge headers of suspect keywords.
Add file with MaxImDL5 header for testing keyword purging
Test of purging bad keywords
PEP8 compliance changes.
Propagate change in add_overscan to reduction tests
Add purge of bad keywords to patch_headers
Change run_patch to reflect new patch_headers.