webadmin: Remove VM comparators in Common.gwt.xml

Removed VmsComparer's and VmsComparerByDiskSize from Common.gwt.xml,
as these classes are not used by the frontend and just add redundant
overhead on GWT's compiler.

Change-Id: I3280f8dd80e24c40891f0f9474388abf478ccce3
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Introducing the comparators package

org.ovirt.engine.core.common.businessentities includes several
comparators, which aren't really business entities on their own right.

This patch introduces the package
org.ovirt.engine.core.common.businessentities.comparators and moves
those comparators there, in order to make the project's organization
more straightforward.

Following patches will move additional comparators there, from other
sub-projects.

Change-Id: I70f2432df8338c736d9ab0e6c97e38acf3ddf92f
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: unify and move Disk Comparators

Organized the various Disk and DiskImage comparators in a sensible
manner.

1. Moved DiskImageByDiskAliasComparator from the dal module to the
   common module, so it could be shared between modules.
2. Removed ImagesComparerByName which had exactly the same
   functionality as DiskImageByDiskAliasComparator, and used it
   instead.
3. Converted DiskImageByBootComparator to be an inline class of
   VmInfoBuilderBase, as it seems useless outside it

Change-Id: Ide5808ba4404d141f43911945e19f170e9694da4
Signed-off-by: Allon Mureinik <amureini@redhat.com>