core: pre-defined weight modules

To be compatible with former scheduler.
* none -> should use evenly distributed
* even distribution -> weight will be calculated according
to cpuLoad, is_spm (config), avg vm consumtions (config),
vm's cpu count and host core count.
* power saving -> host with no vm will be less likely to be
selected, other hosts will be sorted (desc) by even distribution logic.

Change-Id: I55cf5014bc472bf1e126a9737829e7fcf7e21853
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>