Improve Spring support

[RobbinBaauw]

This will improve Spring support a lot. Closes #437.

The following cases are improved:

• Generics resolving in both the return type and method arguments. I did this by switching from the Spring resolver to Typescript Generator's own generic resolver. This also fixed the fact that enum mapping didn't yet work (Map from enum #421)
• PathVariable being string when used without value. In Spring it is possible to use PathVariable without a value if the URI part is the same as the variable name. Now this wasn't checked, leading to PathVariables which were string (default) instead of the required type
• Inheritance giving double methods (could be useful for JAX-Rs too), I did this by looking in the inheritance chain and looking which methods override other methods and add a RequestMapping annotation. If they do that, use it, else use the method of the child type.

[vojtechhabarta]

Thank you very much for this pull request and description of changes.
I went briefly through changes and it looks very useful, Spring support in typescript-generator will be more consistent with Spring behavior.