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)
I originally modified it to Approach 1 but opted instead for removing the function entirely as: 
1) this is inline with what the Couchbase code does
2) didn't like the logic repeated (if local, then .m2, else remote_url) in every build.gradle file. for this point, I would argue that it makes the build more stable :)

You can continue to have your own copy of gradle.properties in either the project build dir or the gradle user home which is what we already do for the thali/Production/build.gradle properties.