Support servlet filters.

 * Deprecate @QueryParam and @BodyParam. Added @Param. We should'nt split these two parameters. Servlet API don't support it.
 * Deprecate `Controller#getRequest()`. Added `Controller#getServletRequest()`. Since Servlet API 3.1+ is good enough for us. We shouldn't wrap it.
 * Deprecate `Controller#getPathParameters()`. Added `Controller#getPathParams()`. Since the `Parameters` class is needed for compatibility with `WebRequest#getQueryParameters()`. But it's deprecated. We should use plain java.util.Map class.
Added test case
Merge pull request #15 from tokuhirom/param

Support servlet filters.