Dirac solver

The python version of bound constrained LBFGS is added and ready for testing (will be moved to C in the meantime). To build with libdirac, use cmake option -DLIBDIRAC_PREFIX=/path/to/libdirac/install

idg-cal/CMakeLists.txt

@@ -10,6 +10,7 @@ install(
         idgcaldpstep_phase_only.py
         idgcaldpstep_phase_only_bfgs.py
         idgcaldpstep_phase_only_dirac.py
+        lbfgsb.py
         idgcaldpstep_rapthor.py
         basisfunctions.py
         idgcalutils.py