In Web Client, use jQuery.ajax() to upload files

If we use FormData and jQuery.ajax() calls to upload a torrent,
we can stop bundling the jquery.form.js module. In addition, this
simplifies passing arguments in the headers s.t. rpc-server.c doesn't
have to look for the CSRF token as one of the multiparts.

This changes the upload POST behavior, so give it a new name (upload2).
The old function (upload) will be deprecated but kept until 2.90 so
that third-party web clients using the old POST semantics will have
time to update.

Bug #5290 <https://trac.transmissionbt.com/ticket/5290>

web/javascript/remote.js

@@ -124,6 +124,18 @@ TransmissionRemote.prototype =
 		});
 	},
 
+	getFreeSpace: function(dir, callback, context) {
+		var remote = this;
+		var o = {
+			method: 'free-space',
+			arguments: { path: dir }
+		};
+		this.sendRequest(o, function(response) {
+			var args = response['arguments'];
+			callback.call (context, args.path, args['size-bytes']);
+		});
+	},
+
 	changeFileCommand: function(torrentId, fileIndices, command) {
 		var remote = this,
 		    args = { ids: [torrentId] };