`doc` dir isn't used by anymore, so removing
RTE sever value for newly controls, fixes #868
- issue: on switch, previousServerValue is empty string
  - serverValue is from ORBEON.xforms.ServerValueStore.get(controlId)
- what happens: when adding an RTE, ServerValueStore.set is called twice
  - in AjaxServer, when handling the control element
  - in AjaxServer, after the update, in case the HTML changes when set
    - at that point the value is empty as the control doesn't exist
- solution: in RTE.coffee set server value after setting it in RTE
Minor: typo