Update USAGE.md

adapted USAGE to reflect the changes to the code, most notably the maximum degree of freedom
code now restricts the maximum number of degrees of freedom to the number of bands with (a useful amount of) data.
Some user specific input to switch this feature on and off and to define what 'is a useful amount of data')
adapted example setup
changed version number to 2.1.4
Merge branch 'develop' of github.com:MegaMorph/galapagos into develop
renaming of galfit_version in output table to be consistent with Galapagos_version. Minor changes.