[DEV] New `less` terminal abilities.

FITSHeaderGroups returns .table() properly now.
[DEV] Support for non-homogenous output tables with list files
[DEV] Adding 'head' command to view headers
[BUG] Fixed a header printing bug
[DEV] Fixing starlist super() calls
[VER] Version bump to 0.2.1
Merge branch 'release/0.2.1' into develop