Create new error message for unsupported TOSCA types

TOSCA-Parser should keep the definition file up to date with spec. For any reason if a full support in code can not be provided due to time constraint or other reason, it should reflect that when user try to parse such a TOSCA type or entities.
At high level, the work includes,
1. Create a file that can contain a list of types that are not supported for parsing at a given point of time.
2. Create a new error type, something like, UnsupportedTypeError
3. When parse template for a type that's listed in the unsupported type file, raise an error something like, UnsupportedTypeError: Type 'xyz' is valid but not supported at this time".

For a somewhat similar type of work in heat-translator refer to the, https://blueprints.launchpad.net/heat-translator/+spec/unsupported-type-validation