[DCOM-96] proxy generation

this is a rebased version of #187 
note that this would bump our required version of Doctrine Common to 2.4, which would also mean we need to bump the required version for Jackrabbit Doctrine DBAL

before merging we should therefore think hard if we want to do this as it would delay the date at which we can move this repo to stable.

aside from this we should double check if this doesnt have some hidden BC breaks.