#20 support ambi dihedral angle restraints from e.g. CYANA

[jurgenfd]

Eg.
support ambi dihedral angle restraints from e.g. CYANA
501 HIS PHI -175.0 75.0 5.00E-01 type=2
501 HIS PSI -75.0 185.0 5.00E-01 type=2
501 HIS PHI -255.0 -25.0 5.00E-01 type=2 OR
501 HIS PSI 25.0 55.0 5.00E-01 type=2
501 HIS PHI -135.0 75.0 5.00E-01 type=2 OR
501 HIS PSI 105.0 185.0 5.00E-01 type=2
which restraints to three regions in the Ramachandran plot.