Hartree-Fock and hybrids in the SCF

The implementation in ADF of the calculation of exact exchange (Hartree Fock exchange) during the SCF, which is also needed for the hybrid functionals, is based on work by Watson et al. J. Chem. Phys 119: 6475 (2003). Implemented are Hartree-Fock, B3LYP, B3LYP*, B1LYP, KMLYP, O3LYP, X3LYP, BHandH, BHandHLYP, B1PW91, MPW1PW, MPW1K, PBE0, and OPBE0. The use of the DEPENDENCY key is necessary at the moment, (and sometimes the ADDDIFFUSEFIT key). Not (yet) available for geometry optimizations, TS, IRC, LT, NMR, EPR g-tensor, TDDFT, frozen cores.