Update and implement the three balancers - even, even guest and power saving

This updates the balancedMemory rule and ties it to the
OptimalForEvenDistribution policy unit.

Two other balancers are added:

consolidatedMemory tied to OptimalForPowerSaving PolicyUnit
tries to keep the number of occupied hosts at minimum

and

balancedVmCount is the equivalent of OptimalForEvenGuestDistribution
PolicyUnit

Change-Id: Idb2e75c2aa0083232d3e1a1a28ffa8b81cebb956
Signed-off-by: Martin Sivak <msivak@redhat.com>