Some methods of the KpointsData to analyze the Bravais lattice
and set k-point paths based on that analysis, contain bugs for
more complicated cell structures like monoclinic and triclinic
cells. A proper implementation can be found in the Seekpath
package. In prepartion of moving towards using this package, we
deprecate the broken methods and move them to a legacy file in
the aiida.tools.data.array.kpoints folder. For the time being
the original methods will still refer to the original implementation
with a deprecation warning that will be emitted.

This was done for consistency with the upcoming implementation
of the Seekpath package to generate high-symmetry kpoints paths.
The following name changes were applied:

	* get_special_points -> get_kpoints_path
	* set_kpoint_path -> get_explicit_kpoints_path

Since the old interface in aiida.orm.data.array.kpoints still
uses the old method names that just pipe through to these
legacy functions in the tools subdirectory, all old behavior
will remain the same.

…ethods

There are two new methods in aiida.tools.data.array.kpoints:

	* get_kpoints_path
	* get_explicit_kpoints_path

These functions will get a path along high-symmetry points and
a list of explicit points along that high-symmetry path, respectively.
By default they will use the Seekpath library, but the user can with
the input 'method' toggle the use of the deprecated legacy implementation.

The return tuple is changed to return exactly the same tuple as
the get_kpoints_path, with two more added return values:

	* explicit_kpoints: a list with explicit kpoints
	* labels: a list with the kpoint labels

Also made sure that the cartesian input flag is passed properly
to the calls of get_kpoints_path that the function makes

We copied to tests of the KpointsData class and changed them
such as to go through the new legacy wrapper interface that
replaced the deprecated KpointsData methods. This verifies
that the wrappers for the 'legacy' method implementation
still expose the same functionality and work the same

conversion of spglib tuple to AiiDA and viceversa,
renamed method from seekpath_tuple to spglib_tuple that
is more correct and moved in a specific structure module,
and added them in aiida.tools for easier importability.

unittest rather than AiiDATestCase)

improved missing existing documentation