Handle incompatible record in Riak 1.4.0.

This is a port from Riak 1.4.1 to master.

Return badrpc calls with an incompatible message when unable to
determine which versions of nodes are communicating in a mixed-
version cluster.

Switch to macros for record definitions.

Also, suppress information in the UI when detecting this incompatibility
to prevent from the display of NaN values.

Conflicts:
	priv/admin/js/core.js
	priv/admin/js/generated/templates.js
	src/riak_control_session.erl
	src/riak_control_wm_cluster.erl