Add lava.utils.interface
Add lava.utils.interface

This package contains the trivial Interface class that we have
in far too many places. It simply hides the ugly __metaclass__
assignment in a less-scary Interface base class. The goal
is to use the standard libary's abc module easily without
having to remember about meta-class definition.


OSSystems/lava-server,Linaro/lava-server,OSSystems/lava-server,OSSystems/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server