Updated documentation to specify angle unit

[mariapana]

The PR aims to clarify which angle unit functions use, since there are some that use radians and others that use degrees. Based on the current documentation alone, a new user may not be certain what the correct input/output should look like. After researching the topic and looking into the function definitions, I added notes on what angle unit was used for each related function.

The modified files are:

src/geometry/rotation_specialization.rs
src/base/matrix.rs

Based on: dimforge#1234