engine: Forbid Bootable and Shareable Disks

A disk cannot be both bootable and shareable.
Changes have been made in the backend and frontend.
Also, an SQL script was added to packaging/dbscripts/upgrade.

Change-Id: I8e221d6534b71db96d0c58442220d249b305079b
Bug-Url: https://bugzilla.redhat.com/1084103
Signed-off-by: Idan Shaby <ishaby@redhat.com>