[Dev] Big checkin: extensive refactoring necessary to support new sidebar design

[John Anderson]

I've been working on the "trees of blocks" change (a dependency of the 
new sidebar design) for way too long -- mostly because it surfaced lots 
of bugs. Rather than finish every last bug, which would take a lot more 
time, Katie and I decided it would be better to check in my changes 
rather than postponing my check in any longer.

So, be aware that there are still a variety of minor problems that 
remain. Most of the problems I've found relate to the fact that all the 
blocks in the UI are now copied to the soup -- so bugs with clouds 
definitions, repository copying or parcel xml copying may not give you 
the block you expect. Rendering and unrendering trees of block surfaced 
a number of subtle bugs. Now that ItemCollections now live in the 
sidebar instead of Views caused a number of problems. Any tree of 
blocks, e.g. the block demo that hard codes paths to the read/only part 
of the repository will fail now that trees of blocks are copied to the 
soup. How sharing hooks up to the sidebar still needs to be integrated 
with Morgen's new sharing design. Bryan and I still need to reconcile 
our different way we plug in a tree of blocks. The tabbed blocks, are in 
the middle of being refactored to use trees of blocks.

Please let me know about any bugs you find and I'll try to get the 
remaining problems fixed as soon as possible.

John