core, webadmin: Remove TabType

The TabType enum is not used anywhere in the codebase, and thus should
be removed.

This patch removes it and any localization references to it.

Change-Id: I2e17e4e533439d9038654213d2f5375c16b24f0a
Signed-off-by: Allon Mureinik <amureini@redhat.com>