Necessary step for switch sync. We can't use
IFloodlightProvider.getSwitches() anymore. We now have a getSwitch()
method. There are also methods to get all dpids (getAllSwitchDpids())
and to get a map (getAllSwitchesMap()). These two return a snapshot.
TODO: need to check if they are used under the correct assumption in
existing code.

First stab at SwitchSyncRepresentation, which is the object I indent to
put in the SyncStore.

Conflicts:
	bigfloodlight/src/main/java/com/bigswitch/floodlight/BigOFSwitchImpl.java
	floodlight/src/main/java/net/floodlightcontroller/core/OFSwitchBase.java
	floodlight/src/main/java/net/floodlightcontroller/core/internal/Controller.java

This is a first big chunk of changes and work in progress. It's not
fully tested yet.
* The OFChannelHandler has be factored out into a separate file.
* State handling is now structured by the current channel state. We
implement the state machine as enum. The enum values are the discrete
states and the "events" of the state machines are member methods of the
enum values.
* Changing roles has been localized in the OFChannelHandler, we perform
timeout checking (no reply to role request) opportunisticly when we
receive any OF message. This way we don't need to complex RoleChanger
thread with task queue.

Conflicts:
	bigfloodlight/src/test/java/com/bigswitch/floodlight/tunnelmanager/TunnelManagerTest.java

BSC-3484: Master not always handling EPERM error (https://github.com/bigswitch/bigswitchcontroller/pull/3085)

o IPV4SubnetTrie Enhancements:
    o Method to get the slices (absent keys) of a given key against the trie
    o Updated shortestNonMatchingPrefixLen to use a /32 key
o VirtualRouting Flow Reconciliation Changes:
    o Support for processing slices and generating OFMatchReconcile objects for each slice
o VirtualRouterManager Changes:
    o Store Src IP CIDRs in routing rules within a trie
    o Store Dst IP CIDRs in routing rules within a trie
    o PacketIn Flow:
        o Prefix is calculated as max of the shortestNonMatchingPrefix against the src/dst routing rule subnets and interface subnets
    o Reconciliation Flow:
        o getSlices against the src/dst routing rule trie of the input src/dst CIDR.
        o If no further slices of the input CIDR are generated by the routing rule trie, getSlices against the interface subnets

[BSC-3431] Introduce a REST API for directed-links.  /wm/topology/directed-links/json will now return unidirectional links.

[BSC-3431] Introduce 'direction' as a field in LinkWithType.  The REST API will now return links with direction field that will indicate if the link bidirectional or unidirectional.

BSC-3397 Add IOFSwitch.writeThrottled() (https://github.com/bigswitch/bigswitchcontroller/pull/2991)

Conflicts:
	bigfloodlight/src/main/java/com/bigswitch/floodlight/bvs/virtualrouting/internal/DhcpManager.java

Conflicts:
	floodlight/src/main/java/net/floodlightcontroller/debugcounter/DebugCounter.java
	floodlight/src/main/java/net/floodlightcontroller/debugcounter/DebugCounterGetResource.java
	floodlight/src/main/java/net/floodlightcontroller/debugcounter/DebugCounterResetResource.java
	floodlight/src/main/java/net/floodlightcontroller/debugcounter/DebugCounterStateResource.java

Conflicts:
	floodlight/src/main/java/net/floodlightcontroller/debugcounter/DebugCounter.java
	floodlight/src/main/java/net/floodlightcontroller/debugcounter/IDebugCounterService.java