Set bnd_repourl gradle property into Workspace

This allows the repo url to be externally set in the CI build with the
gradle command line option -Pbnd_repourl=<url>.

Signed-off-by: BJ Hargrave <bj@bjhargrave.com>
Merge pull request #940 from bjhargrave/set-repourl-from-command-line

Set bnd_repourl gradle property into Workspace