- updated 3.12 news a bit
- added derived units to the index
- use gwy_derived_quantity() to keep all the unit information (mostly) out of the module
- fixed a typo
- corrected comments in gwy_field_psdf_to_angular_spectrum() and renamed a few things
- added some notes to angular spectrum, which seems to have the wrong units
- removed fixed units
- actually added the derived-units source files