End-to-end dependencies Merged

Currently, all dependencies in Aha! are of End-to-Beginning type, e.g. "Feature A needs to be done before I can start feature B".

However, this imposes an unnecessary restriction and forces sequential work as opposed to parallelized work. More often, one can start work on a dependent feature before finishing a dependency. Standard project management sw supports end-to-end dependencies, e.g. "Feature A needs to be finished before I can finish Feature B".