properly integrate gquad

[sjanssen2]

open TODOs for #60

• define covariance for gquads in Algebras/alg_ali_purecovar.gap, Algebras/Probing/Parts/algpart_probing_gquad.gap
• define hi_shape definitions in Algebras/Shapes/alg_ali_hishapes.gap and Algebras/Shapes/alg_hishapes.gap
• check against RNAfold how probing parameters get applied to gquads in Algebras/Probing/Parts/algpart_probing_gquad.gap
• how could gquads be integrated into macrostate pfunc computation? Algebras/Pfunc/alg_pfunc_macrostate.gap. gquad are not yet added to the macrostate grammar, probably for good
• we might want to allow several mismatches for onlychar in alifold.hh and have this ratio as a parameter?!