Refactoring: moving methods that parse topology from SDNLink to BaseSDNTopologyService
Organizing SDN* object capabilities

+ Added class SDNObject, that is responsible for holding attributes
  common to all SDN* objects. At this moment, common attributes to
  all nodes is the list of capabilities (features)
+ Moved SDNCapability enum type to a new file
+ Add VLAN capability to all SDNLinks that have names starting with 00.
Minor: changing a return type to (logically) match name of a method
Minor fixes to README.md
Fixing the default domain name
Changing the Floodlight default link name to "1" instead of "link*"

+ Adding some extra debug messages
Splitting SDNLink class into two (SDNLink and SDNHop) (1/2)

SDN connections are now represented by two distinct classes, one for inter-device links
(represented by SDNLink objects) and one for intra-device hops (SDNHop). Both inherit
from SDNConnection, which holds common attributes and methods.
Splitting SDNLink class into two (SDNLink and SDNHop) (2/2)

SDN connections are now represented by two distinct classes, one for inter-device links
(represented by SDNLink objects) and one for intra-device hops (SDNHop). Both inherit
from SDNConnection, which holds common attributes and methods.
Adding hashCode() to SDNNode class
Minor fix: improving check in equals() method of SDNLink classs
Minor change: improving String representation of SDNHop class