Initial cleanup for massive refactor
[common] added initial interface for base element class.

It is intended for subclasses not to be instantiated directly but
through the factory methods, so hide constructors as thorough as
possible
[misc] added interface for factory element creation methods
[common] added public definitions for all essential classes and respective sets
[common] element data model completed, refactored to use full inline
[include] graph data model complete
[common] added set operations to perform elements filtering
[common] added path abstraction
[common] Refactored to use static criteria class to work with elements
properties
refactored to use common factory in order to support json serialization
Initial resources readout
Full xml readout, see /assets/initial_test/simple.dcxml for a new syntax tree
finished xml writeout with loosely coupled requests
Resource vector parsing with specified types is implemented.
File is forgotten.
[routing] Initial infrstructure for generalied routing
[routing] Added BFSQueue searching environment
Prototype of bfs router, no backtrack
Supportive class refactor follows
New elements and features are added according to new tenant model: parameter, port, vnf, service as user, service as provider.