Change method names in Spring convenience class

Users will find it more friendly and easier to remember if all they
need is a static import and a method called "spring" (as opposed to
having to remember 2 method names, one of which is "run" which could
mean anything).

E.g.

ratpack {
   handlers {
     register spring(SampleSpringBootApp)

     handler("foo") { String msg ->
       render msg
     }
   }
 }
Merge pull request #445 from dsyer/feature/spring-static

Change method names in Spring convenience class