Fix opening ofp_channel and add starting conn_listener

OpenFLow 1.3.2 specification introduces a new statement that OpenFlow
controllers can connect to OpenFlow switches. After adjusting
the ofp_client API there is a need to fix openning the ofp_channel
in linc_logic. The module listening for connections from switches
is also added and started by linc_logic.
(FlowForwarding/LINC-Switch#147).
Add functionality allowing the controller connecting to a switch

OpenFLow 1.3.2 specification introduces a new statement that OpenFlow
controllers can connect to OpenFlow switches actively. Now
the of_controller_v4.sh can be started with an option simulating such
behavior.
(FlowForwarding/LINC-Switch#147).
Introduce config parameter for controllers listener; refactor linc_logic

OpenFLow 1.3.2 specification introduces a new statement that OpenFlow
controllers can connect to OpenFlow switches actively. Config parameter
`controllers_listener` is introduced to support this functionality.
By the way linc_logic module is refactored regarding this functionality.
(FlowForwarding/LINC-Switch#147).
Introduce checking if linc_logic process is alive between linc:start/stop

While running the tests it turned out that linc does not have enough
time to start. Now some checking is introduce to delay stopping the app.
(FlowForwarding/LINC-Switch#147).
Merge pull request #187 from FlowForwarding/issue147

Support controllers actively connecting to the switch