BibCheck rule to move additional TexKeys from a to z

Signed-off-by: Kirsten Sachs <kirsten.sachs@desy.de>
BibCheck rule to move one TexKey from z to a if there is no a

Signed-off-by: Kirsten Sachs <kirsten.sachs@desy.de>
rules added: mvtexkey_a2z, mvtexkey_z2a

Signed-off-by: Kirsten Sachs <kirsten.sachs@desy.de>