initial release of output status restore

implemented framework for output status restore
implemented bko-plot output status restore
save/restore status for combined plots
implemented table state saving
use command as well as control

mac users will be happy
added comment
reorganized keyboard shortcuts

better support for windows and mac specific bindings
implemented undo/redo for delete notebook cells
Merge pull request #770 from twosigma/ildipo/issue-220

use command as well as control
Merge pull request #768 from twosigma/ildipo/displaystate

Ildipo/displaystate
remove debug logging
merge
cell body expansion

cell body is now saved (and read) as array of strings to support
diff-ing models
Merge branch 'master' into ildipo/jsonformat
do not copy default notebook
changed highlight for data tables
Merge pull request #780 from twosigma/ildipo/dtlookandfeel2

changed highlight for data tables
transform only cell body
added file search dirs for notebook load
Merge pull request #783 from twosigma/ildipo/filesearchdirs

added file search dirs for notebook load
Merge pull request #775 from twosigma/ildipo/jsonformat

Ildipo/jsonformat