gateone.py:  Moved the bits that set 'cls.prefs' from ApplicationWebSocket.open() to ApplicationWebSocket.initialize().  This should make prefs available earlier in the chain of events (so applications can use them for say, deciding which plugins to load).
gateone.py:  Added an optional keyword argument to send_js_or_css():  element_id.  If provided the client will be instructed to name the created <script> or <style> element with the given ID (it will still use the prefix).
gateone.js:  Updated GateOne.Utils.loadJSAction() and GateOne.Utils.loadStyleAction() to use the new element_id parameter if available.
app_terminal.py:  The terminal application will *actually* use the new 'enabled_plugins' option if it's set somewhere in the settings dir (apparently my previous commit broke things).