Change vimconn.py to include the interface functions
to be implemented by the specific VIM connectors, in order
to achieve Service Function Chaining as managed by a VIM.
This relates to feature 638.
Change-Id: I3b5c35ad5b2ca6e4cdd17e5720fbaa13acffc4e1 Signed-off-by: Igor Duarte Cardoso <igor.duarte.cardoso@intel.com>