Removed "*_preserve" traces and duplicate function. Removed deg

arguments

- Tidied up the comments/documentation to remove all traces of the
originally version of the PR which included float promotions.
- Removed the duplicate angle function
- Removed the deg parameter in the various functions. This leaves the
conversion up to the user and can easily be achieved with the
Float::to_degrees function
- Tidied some trait bounds which did not need the FloatConst trait
- Ran ``cargo fmt``

Author: jmg049