DFTB: added DFTB3 diagonal correction, two regtests;
DFTB: allows for Grimme D3 dispersion correction (c6 and c8 only), three
regtests;
NDDO: allows for Grimme D3 dispersion correction (c6 and c8 only), three
regtests;


git-svn-id: svn://svn.code.sf.net/p/cp2k/code/trunk@14195 bac0169d-1eea-4375-b5f6-f89d2ced9994