Selection and document editing goes through the projection using constraint based change propagation.

Changed iomap classes to computed-class.
Changed document->document and document->graphics projections to take care of computed states.
Added subseq to string reference mapping.
Added delete/backspace keys to string domain.
Added preliminary tree editing operation to replace a tree node.
Created separate folders for higher-order and generic projections.
Added iomap definer and renamed file to iomap.lisp
Removed *iomap* and added a new parameter to printers instead.
Added filter for reader/printer when using input/output devices.
Added test walker to force all computed states.
Fixed ASD dependency.
Added quote for value when setting a reference value.
Added some experimental code for computed-state test usage.
Implemented deleting tree nodes.
Changed mapping to always have the same structure.
Factored out control + home/end handling.
Added parent-node argument to indentation provider.
Changed JSON and tree domains to avoid wrapping nodes without compound children.
Changed to all graphic characters to be typed in.
Added line numbering to tree tests.
Added some preliminary tree operations: move node up, wrap node, transpose node, delete node, insert node.
Added handling compound operations to document->document reader.
Added selection updates to some string editing operations.