Implement All_All_Interface communication for edges

This is hardly tested -- please handle with care.
Remove the 'strategy' parameter from the loadBalance method

I finally figured out what it does: nothing.  Or rather, it used to control
the Chaco grid partitioner built into UG.  However, we ripped out the Chaco
code for licensing reasons quite a while ago, and the parameter has been
obsolete ever since.
[cleanup] Merge two loadBalance methods into one
[cleanup] Simplify the load balancing methods that uses the internal partitioner