Make function to check if two clusterings are a permutation of each other

[epurdom]

This code has basically already been written in clusterManyTest.R -- just needs to be converted into proper function.

Also a function to change the internal ids so that if they are exact match then get the same clusterIds. Again, already written as part of first test, so might as well give option. Main question is what to do with clusterLegend info. Probably user option to copy over the clusterLegend info as well.