Added generation of Transfer Objects from Type Definitions.

Added generation of Transfer Objects from Type Definitions.

Extended functionality of Type provider to resolve Type Definitions in schema context as GeneratedTransfeObjects with proper package names and
class names;
Updated generateTypes in BindingGeneratorImpl to generate also Transfer Objects from Type Definitions;
Added BindingGeneratorUtil to replace functionality of CodeGeneratorHelper;
Modified EnumerationBuilderImpl - changed visibility from package protected to public due to need for generation of stand alone enums;
Refactored GeneratorUtil with use of BindingGeneratorUtil methods;

Fixed bug in where SchemaPath was incorectly generated for yang types in yang-model-util project;

Changed YangModelParser API - removed parseYangModel method and changed parseYangModels param from vararg String to List of Files and from vararg InputStream to List of Input Streams;

Modified YangToSourcesMojoj and GenerateSourcesTest in maven-yang-plugin due to change in YangModelParser API;
Modified YangToSourcesPluginTest due to change in YangModelParser API;
Modified Demo in binding-model-demo due to change in YangModelParser API;
Modified GeneratedTypesTest in binding-generator-impl -> changed load of yang files due to change in YangModelParser API;

Added comment generation for interface and class definition in binding-java-api-generator -> GeneratorUtil;

Change-Id: Id1be574e10f7f80d1badfbdec2bcc4a98564fee5
Signed-off-by: Lukas Sedlak <lsedlak@cisco.com>