this fixes a bug where navigating to the next/previous card using
shortcut keys resulted in the first field being clobbered
- get rid of the stealFocus option in favour of explicitly passing
focusTo to setNote()
- setFields() is no longer responsible for setting focus
- add focusTo var to the browser so that the row changed hook can
restore focus when navigating to next/previous card
- fix the row changed hook being called twice
- the blur event now includes the field number instead of relying on the
editor to have the correct currentField
- the current field is set to null on blur
- use deferred js and a callback rather than keeping track of when we
were loaded
- add shift+tab shortcut to go to previous field
- js code that was previously bundled in .py files is now in the
web folder
- add helpers to create links to bundled files, and update
stdHtml() to accept a list of javascript files to include
instead of text
- render MathJax in card layout and preview screens - these should be
updated in the future to update the document dynamically like the
reviewer does
- start media server earlier so it can be used to serve content for
the toolbar, etc
- work around a bug in WebEngine on Windows that could cause the
media server to hang
