restapi - #755579: Return proper http status for errors

Until now all engine failures resulted in 400 BAD_REQEST.
Infrasctructure was added to return proper error messages,
depending on the exact failure.

Error types have been added to enum entries in VdcBllMessages.
The file has been moved from 'dal' module to 'common' module
so that API layer will have access to it.

Bug-Url: https://bugzilla.redhat.com/755579
Change-Id: I395e4b303eda174360ece709ddd7de6b1e3ce93f
Signed-off-by: Ori Liel <oliel@redhat.com>