re-write old doc/README to something more useful and up-to-date
artifacts
clear old event handlers when enabling/disabling checkbox menu item

fixes #257
add alt-enter execute line or selection behavior to cells

completes #139 (for real now)
reselect notebook node on starring, if it was

(kind of silly)
fixes #232
Minor fix for mhas crashing if an attribute exists but is undefined
Merge branch 'release/0.9' of github.com:/cscheid/rcloud into develop