GUACAMOLE-221: Prompt user to provide additional parameters when "required" instruction is received.

guacamole/src/main/webapp/translations/en.json

@@ -54,7 +54,9 @@
     "CLIENT" : {
 
         "ACTION_ACKNOWLEDGE"               : "@:APP.ACTION_ACKNOWLEDGE",
+        "ACTION_CANCEL"                    : "@:APP.ACTION_CANCEL",
         "ACTION_CLEAR_COMPLETED_TRANSFERS" : "Clear",
+        "ACTION_CONTINUE"                  : "@:APP.ACTION_CONTINUE",
         "ACTION_DISCONNECT"                : "Disconnect",
         "ACTION_LOGOUT"                    : "@:APP.ACTION_LOGOUT",
         "ACTION_NAVIGATE_BACK"             : "@:APP.ACTION_NAVIGATE_BACK",