This commits also implement the query reform from #608. It also consists
of many, many breaking changes. Among them are:
* Query parts in route paths use new query reform syntax.
* Routing for queries is now lenient.
- Default ranking has changed to reflect query reform.
* Format routing matching has been fixed.
- Routes with formats matching "accept" will always collide.
- Routes with formats matching "content-type" require requests to
have an equivalent content-type header to match.
- Requests with imprecise content-types are treated as not having a
content-type.
* Generated routes and catchers respect visibility modifiers.
* Raw getter methods from request were renamed and retooled.
- In particular, the index parameter is based on segments in the
route path, not dynamic parameters.
* The method-based attributes no longer accept a keyed 'path'.
* The 'rocket_codegen' crate is gone and will no longer be public.
* The 'FormItems' iterator emits values of type 'FormItem'.
- The internal form items' string can no longer be retrieved.
* In general, routes are more strictly validated.
* Logging from codegen now funnels through logging infrastructure.
* Routing has been optimized by caching routing metadata.
Resolves#93.
Resolves#608.
Resolves#693.
Resolves#476.
