gateway: make runs api related to project/user

[sgotti]

Currently the gateway runs api are queried by the run id. The run id is meant to be a global sequence. From the user perspective or for other reason explained below it could be better to reference them by their project reference (i.e "org/org01/proj01", "user/user01/subproj/proj01") or user (for user direct run i.e. "user/user01") plus the related project run number (a sequential counter per project/user)
This is much more cleaner and could help for future improvements

*: Shard projects/users to multiple runservices. With the gateway currently receiving only a runid we cannot know which runservice owns a project/user.
*: Remove the need for a global (per runservice) sequence.

This will require changes also to the ui at https://github.com/agola-io/agola-web

I'm already working on it.

[sgotti]

Implemented in #323