This is to make people prefer the functional style.
Things like `a.dot(b)` dont make sense per se (there is no reason for `a` to have a different
status than `b`). Using static methods avoid this.
In-place methods are left unchanged.
Everything changed, hopefully for the best.
* everything is accessible from the `na` module. It re-export
everything and provides free functions (i-e: na::dot(a, b) instead of
a.dot(b)) for most functionalities.
* matrix/vector adaptors (Rotmat, Transform) are replaced by plain
types: Rot{2, 3, 4} for rotation matrices and Iso{2, 3, 4} for
isometries (rotation + translation). This old adaptors system was to
hard to understand and to document.
* each file related to data structures moved to the `structs` folder.
This makes the doc a lot more readable and make people prefer the
`na` module instead of individual small modules.
* Because `na` exists now, the modules `structs::vec` and
`structs::mat` dont re-export anything now.
As a side effect, this makes the documentation more readable.
Trait failes are merged in three files:
* operations.rs - for low-level matrix/vector operations
* geometry.rs - for operations with a clear, broadly known geometric meaning.
* structure.rs - for operations to access/alter the object inner structures.
Specialisations are moved to the `spec` folder.
