Added workaround for PyQt/uuid crashes.

Fixes #775.
Fixed pollution of GafferUI namespace with IECore module.

Also added the Gaffer import that must be made before _GafferUI can import (due to order of boost::python::class_ registrations) so that it is no longer for programmers to do that themselves.
Merge pull request #778 from johnhaddon/uuid

UUID/PyQt crash workaround