Package as both 'configshell' and 'configshell_fb'

We have changed the API from Datera configshell, so we should be using
a different package name to eliminate confusion.

Still package under configshell pkg name, but issue a warning to switch.

Change code in shell.py to use relative imports instead of package name.

Signed-off-by: Andy Grover <agrover@redhat.com>