webadmin: Disk dialog - capitalize labels

New/Edit disk dialog:
s/Is bootable/Is Bootable
s/Is shareable/Is Shareable
s/Wipe after delete/Wipe After Delete

Change-Id: Ibb6adaeed3e7e8ce99fa73730e43896355027efe
Signed-off-by: Daniel Erez <derez@redhat.com>