factored management of individual switches to a separate module

OpenFlow0x01_Platform used to manage connections to each switch *and*
maintain a table of all switches. The OpenFlow abstraction layer needs
code to manage individual connections. But, its table of switches will
have a different type, since it must manage both 1.0 and 1.3 switches.

The abstraction layer will be able to use the new OpenFlow0x01_switch
module and OpenFlow0x01_Platform will eventually be phased out.
oasis setup