core: RunVmCommand.canDoAction cleanup (1)

Inital commit includes adding a new class 'RunVmValidator';
Eventually, run vm validations will be
extracted to this class, and VmRunHandler will be removed.

This patch includes moving custom proerprties validation to
the validator and matching tests.

Note: RunVmValidator will have a deprecated static method
compatible to the old one, to avoid regressions in an
exsisting VmPoolCommandBase static reference.

Change-Id: I60bbdb54d150878123968893c23169de253e1ba2
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>