Use default comparer for sorting supports in DiscreteHistogram

[kimsey0]

This is for example relevant for StandardDiscreteUniform, which changes from

 0|***************************************
 1|***************************************
 2|**************************************
 3|***************************************
-1|***************************************
-2|***************************************
-3|****************************************

to

-3|****************************************
-2|***************************************
-1|***************************************
 0|***************************************
 1|**************************************
 2|***************************************
 3|**************************************

[kimsey0]

This requires, of course, that T implements IComparable. I made the pull request quickly after #1. I'll just fix that.

[kimsey0]

There we go. Now it casts to IComparable and defaults to ToLabel. (The check could of course be moved outside of OrderBy to do it fewer times, but it doesn't make much of a difference for the number of samples here.)