When a ProjectorShell is created it creates a view of the full
projector array with orbital 'ilm' and band 'ib' indices interchanged.
The reason for this is that this corresponds more naturally to the
definition of the projector P_{m\nu} and also allows for multiplications
of projector matrices without additional transposition.
The tests have been modified accordingly.
A preliminary test suite for class 'ProjectorGroup' was added.
Currently, only a simplest test is performed testing that
after the input is processed the resulting projectors selected
within a given energy window are corret.