Allow configurable version numbers for binaries

* Use system properties to set version number, maven remote repo, maven
credentials
* Remove gradle.properties as gradle prioritizes those system properties over those supplied over the command line (which is stupid)
To the best of my knowledge we don't use this function, ever. It's just used for their WebDAV based maven server and ours doesn't work that way. Ideally I'd like us to not touch code we aren't using so merging back with CouchBase is as easy as possible. So can you undo this change?