Portals; Theming enhancements

The following Theming related changes have been made to Portals:
* Resources now respect a special suffix of '.theme', e.g., 'TEST.theme'
* These resources now appear in a special 'Theme' folder on the IDE page
* When importing a Portal, you now have the option of preserving any of your existing Resources with a '.theme' suffix
* The 'Theme' page of the Portals form now allows a 'Theme' to be specified
* Resource tags can now include a special replaceable '[THEME]' tag that is replaced based on the defined Theme
* The 'Theme' page of the Portals form now allows a 'Inline Resource' to be specified for the Login form
* This will be resolved into a <%Resource%> tag and can hence contain the "[THEME]" tag, e.g., <%RESOURCE:[THEME].theme%>


This allows resources to be varied without having to update the page, e.g., if you include the following at the bottom of the Master Page:

<%Resource:[THEME].theme%>