Writing vectors as strings is very common and should belong to `vector.*`. `minetest.pos_to_string` is also too long to write, implies that one should only use it for positions and leaves no spaces after the commas.
* added vector.rotate
* added vector.forward_from_rotation and vector.up_from_rotation
* added vector.forward_up_to_rotatiton
* fixed some bugs and formatting with vector functions
* shortened name of some new vector functions and added documentation
* made vector.rotate not require a unit vector as axis
* fixed crash with vector.forward_up_to_rot
* renamed new vector functions, made vector.rotate apply a rotation matrix, old vector.rotate is now called vector.rotate_around_axis
* documented vector function changes
* removed some whitespace to appease luacheck
* implemented and fixed optimization of vector.rotate_around_axis by SmallJoker
* added some unit tests for rotation vector functions
* clarified that rotation vectors are in radians and according to the left hand rule
* hopefully appeased luacheck
* renamed rotation_to_horizontal to forward_at_rotation, rotation_to_vertical to up_at_rotation
* handled cases where sin or cos are 0 in rotation vector functions
* added more comments
* clarified documentation of rotation vector functions
* added more unit tests
* changed way in which vector.rotate_around_axis is adjusted for left handed coordinate systems
* made vector.rotate_around_axis actually left handed
* unrolled matrix multiplication
* removed vector.forward_at_rotation and vector.up_at_rotation
* prettified vector.rotate_around_axis, made previous commits not break anything
* removed references to removed vector.forward_at_rotation and vector.up_at_rotation
* removed documentation of removed vector functions
* clarified documentation and fixed styling of rotation vector functions
* restyled comments minorly
* spelling fixes and some hopefully better comments
* allowed 'up' to be missing from vector.directions_to_rotation and removed requirement for unit vectors as arguments
* made vector.rotate_around_axis() right handed again for consistency
* documented previous changes
* made matrix multiplication actually multiply
* renamed vector.directions_to_rotation() to vector.dir_to_rotation()
* optimized a distance comparison
* Fixed potential false positive in unit tests.
Co-authored-by: NetherEran <nethereran@hotmail.com>
