* Only dispatch OF messages to listeners if the switch is in the active
  switch map (and is in MASTER role and connected).
  Fixes BSC-2829
* When transitioning to MASTER: notify IHAListeners of role-change
  before starting dispatching messages. When transitioning to SLAVE:
  stop dispatching before notifying IHAListeners.
  Fixes BSC-2407

When injecting fake ARP: set sender IP to 0 (ARP probe)
Remove weird IP learning on DHCP-replies:
	WILL BREAK DHCP MANAGER WITH RELAYS

Merge into master from pull request #1907: Implement BigOFSwitchImpl, default BigFloodlight switch driver (https://github.com/bigswitch/bigswitchcontroller/pull/1907)

Having "? extends OFStatistics" instead of "Statistics" allows for
typesafe assignment of sub-statistics

BSC-2836

This is a short-term. In the long run we actually do want to prevent
learning on these ports.

BSC-2836

split up in multiple messages if too many flows
Also add a MAXIMUM_LENGTH constant to OFMessage

BSC-2837: When returning early from learnDeviceByEntity: process
	deleteQueue
BSC-2836: Do not learn entities on internal ports
BSC-2834: Some device updates get queued before check for concurrent
	modification
BSC-2824: Remove potential incorrect Corrupted Device Index exception