make rest controller more generic to support additional workflows

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #116
| License       | MIT
| Doc PR        | TODO

/cc @uwej711 

btw for the doc, this is using symfony http handling, meanign X-HTTP-Method-Override is supported as well.
> with the route definition we open a very large door for people to pass
> through. while createphp may validate the method, imho its problematic
> to open a door that is validated at a lower level only. so this is just
> about security.

so do we need to expand on the AccessChecker (i guess it should use
voters like the security checker of symfony) and have a way to configure
the allowed methods?

that just feels very cumbersome when we don't have the workflow tag yet.

also, we just pass the name of that method on to the RestService so i
don't really see such a big problem.

> second I envision that some people will want to not support specific
> workflows/methods (doesn't want to allow to update etc) so it would be
> good to give them config options to control this.

yeah, as i
[said](https://github.com/symfony-cmf/CreateBundle/pull/117#issuecomment-52461314)
there is AccessChecker for this.