Slice cube implementation and serialization tests.
Move tests from serialization into specific package.
First slice implementation including set and contains.
Merge branch 'master' of https://github.com/dana-i2cat/mqnaas into feature/slice-implementation

Conflicts:
	core.api/src/test/java/org/mqnaas/core/api/slicing/SerializationUtils.java
	core.api/src/test/java/org/mqnaas/core/api/slicing/serialization/SerializationUtils.java
	core.api/src/test/java/org/mqnaas/core/api/slicing/serialization/SlicingUnitSerializationTest.java
	core.api/src/test/java/org/mqnaas/core/api/slicing/serialization/SpecificationSerializationTest.java
	test-helpers/src/main/java/org/mqnaas/general/test/helpers/serialization/SerializationUtils.java
Implementation of the Slice.add method.
Implementation of Slice.cut method.
Efficiency tests.
Add more tests for slices and fix bugs.
Improve contains method with Georg's algorithm.
Improve add operation with Georg's algorithm.
Improve cut method with Georg's algorithm.
Modify name of operation.
Improve set and unset with Georg's algorithm.
Add originalSlice information to Slice.
Slice could only be added if its not in operational state.
Add comments to code.
Rename slice to implement the new one. Implement slicing interfaces.
Move Slice from core.api to core. Create SliceAdministration capability interface.
Old slice model moved to new capability, and fix test for new code structure.
Include getCube and getAvailableCubes in SliceManagementCapability.