Uniform page synopses and AJAXed ImageEditor

https://github.com/gunchleoc/ginbeag/issues/24

- All image editing except for newsitem sysnopsis are now AJAXed

- Changed control flow for editing pages, Synopsis & settings now separated from page elements

- Moved classes from admin/includes/objects/elements.php to admin/includes/objects/forms.php

- Adapted radiobuttonform for correct use of JSIDs