use ui buffering in changeset printer delete old uibuffer class delete old stringio class move show to _show add new show that uses ui.pushbuffer to buffer add new flush that writes buffered data add props arg to changeset_printer to match _templater

add a simple nested buffering scheme to ui

make manifest friendlier switch to using context code ..which uses first parent by default show file hashes only with debug switch show permissions with verbose fix up tests