Samples: add memory based load-balancing sample module

Adds a comprehensive example of a memory filter.
Logic stages:
- find the host with the least amount of free memory
- check what is the maximum vm size it can pass to
  the other hosts without overloading them
- find a vm it can pass that is small enough to
  run on one of the other servers.
  If safe_selection = true, return the smallest vm
  else try and find one that will solve the
  overutilization in one migration

Change-Id: I1b4a41064631912f5624723327a2ff5ebf158d5c
Signed-off-by: Noam Slomianko <nslomian@redhat.com>