delete whitespace
indent tree nodes displayed in the data renderer
fix the way the default emitter deals with removed elements of the data model

Only report changes made to the inputs that the emitter cares
about. Some removals will look just like updates. Removals will only
generate :node-delete deltas when something has been deleted at the
input path.
create app model nodes automatically when they do not exist

This change means that we can emit

[:value [:a :b :c :d] 10]

instead of

[:node-create [:a]]
[:node-create [:a :b]]
[:node-create [:a :b :c]]
[:node-create [:a :b :c :d]]
[:value [:a :b :c :d] 10]

The :node-create deltas will be generated automatically if those nodes
do not exist.