JENA-611 : Add LocatorFTP
(RIOT version) LocatorURL becomes an abstract class for LocatorHTTP and LocatorFTP.

git-svn-id: https://svn.apache.org/repos/asf/jena/branches/jena-fuseki-new-ui@1551363 13f79535-47bb-0310-9956-ffa450edef68