Merge branch 'development'
Lots of refinements and bugfixes for the new DB model without an explicit question-types table.
Import ace version
Use ace editor as the code editor
Set editor read-only if text-area is read-only
Merge branch 'mru/ace' of https://github.com/mrud/CodeRunner into development
Incorporate use of Ace code editor (thanks to Ulrich Dangel).