This function is used by triplex.search
function to get
default isogroup tables. These tables correspond exactly with Table 1 published
in (Lexa, 2011) and they represent the isomorphic groups of triplets.
As a common triplet structure is H.WC:WC, to customize isogroup tables
just use H as a row index, WC as a column index, then set desired group number and
pass such modified tables through group_table
option of triplex.search
interface.