Path correction

Two things going on here. First, I conditionalize the Artifactory plugin in the gradle build for those without a artifactoryUrl variable set. 

Second, I cleanup the path before it gets passed to HttpBuilder. The reason is that when it sees a path with two slashes it treats it like a "../" and goes up a level. Our artifactory has a context of "/", so all our paths where looking like this: "//api/storage/libs-release-local/org/acme" which HttpBuilder then munges to "/storage/libs-release-local/org/acme",". This fix is necessary to use the artifactory-client-java library with an artiactory at the root context.