Reorder histogram template parameters

[danhoeflinger]

Reorder histogram template parameters and remove unused default template argument.

One option for specification of histogram (version 1a from email).

[danhoeflinger]

After offline discussion, this version was chosen, as it was determined that we will almost surely break no code by reversing these two template arguments.
If we have some report of bug / break, we have an option in the future to add code to handle deprecated case which requires explicit specification of arguments, but the first response would be to instead instruct users remove their explicit template arguments. If they require explicit specification of types to force some conversion, we can instruct them to add an explicit conversion in addition to removing the specified template types.

[mmichel11]

LGTM

[adamfidel]

Based on the discussion today, LGTM.

[rarutyun]

The changes look exactly how we agreed on. Looks good to me!