Moved redundant/generic code into a new module

A lot of the code used by different drivers was redundant.  This patch
moves redundant/generic code into a new module that is imported by
switch specific driver modules.
Migrated more functions into vlan.py

This commit moves two more functions from dell.py to vlan.py.  In
order to do this, a new section had to be added to haas.cfg called
'vlan', since it needed a driver independant section name.
Added vlan section to deployment.cfg.example
Removed unnecessary imports in dell.py
Merge branch 'devel' into modularize-drivers

Conflicts:
	deployment.cfg.example
Merge pull request #241 from ryabouza/modularize-drivers

Moved redundant/generic code into a new module