#127: Move properties to Edit screen using pre-loaded fieldsets

Currently, the Properties view on a content object is cumbersome to get to – you almost always want to edit it along with the normal properties anyway – and has become a random mix of items that are not important enough to be on the main edit screen - but are important enough to be on the object itself.

We should consolidate these on the edit screen, and have a clickable legend area that can be used to navigate around the different schemata used to represent the item.

• Merge the dhtml-schemata branch, so we can have schemata without reloading the page (if this isn't already done by the time work on this starts).
• Improve the look of the schemata selector
• Group the Properties attributes better, maybe create 2-3 schemata of it if necessary.

• There should be little risk involved in this, since the dhtml-schemata branch requires that you explicitly turn it on, thus the few use cases that require schemata 1 to be filled out before you can go to schemata 2 will still work.
• There is some risk involved with Kupu if we enable it by default, though - there are reported problems since Kupu lives in an iframe. We need to make sure it works, both with editors on different pages and several editors at the same time.

All parts of this are implemented in the plip 127 branches of Plone, ATCT and Archetypes.
The dhtml-schemata branch was not used, instead content types can be marked with the IMultiPageSchema interface to keep the old behaviour.
The properties tab was removed and the metadata schema can always be selected on the edit page for old types.
The javascript and css parts in Plone are done.