Added capability to resolve Enumeration type definitions;

Added capability to resolve Enumeration type definitions;

Added ReferencedTypeImpl for resolving of referenced enumeration types;
Modified GeneratedTypeBuilder for setting correct package name for
enumeration types defined as inner enums in Generated Types;
Modified EnumBuilder added extends of Type interface in
binding-model-api;
Added test case for resolving of Leaf Enumeration in GeneratedTypesTest;

Modified BindingGeneratorImpl accordingly:
Added Implementation to resolve Enumeration type,
The Schema Tree traversal methods removed - replaced by
DataNodeIterator,

Refactored TypeProviderImpl - resolving of leafrefs now through
SchemaContextUtil methods;

Chenged package name in code-generator-demo to
org.opendaylight.controller.yang;

Added DataNodeIterator and SchemaContextUtil into yang-model-util

Fixed Raw TypeDefinition in ExtendedType implementation;
Fixed SchemaPath setting in EnumerationType implementation - added two
parametric constructors that contains SchemaPath parameter;
Updated parseTypeBody method in YangModelBuilderUtil in
yang-model-parser-impl - added Enumeration constructor call with schema
path parameter;
Fixed constructor with XPath parameter visbility in Leafref
implementation;

Added extension of AugmentationTarget for ChoiceNode in yang-model-api;

Signed-off-by: Lukas Sedlak <lsedlak@cisco.com>