Compare same terms in different GeneSetCollections

[llrs]

A user request a method to compare the same GeneSet names of different GeneSetCollections (GSC), by counting the number of genes in each.

Could go on the line of compare(GSC1, GSC2) and then look for same pathways/GeneSet names and compare the number in each case. Could return the total number of shared names and the differences between them in a data.frame.

Would it be expandable to more than two GSC? Yes if in the names of the data.frame we set the names of the GSC being compared and return NA if the term is not shared between two GSC.
Like: Terms GSC1_GSC2 GSC1_GSC3 GSC2_GSC3

[llrs]

The new nested function could be used to compare if different names has the same genes

[llrs]

Solved with 5945b69 in the pairwise manner
But stills need improvements because it depends on Vectorize, see #3