Set height:100% on #dijitEditorBody in addition to <body>.
Note that usually #dijitEditorBody is actually the <div> inside the <body>.

Setting height:100% on the <div> fixes the Chrome problem where typing ctrl-A
and then some characters locks up the editor.   Doesn't seem to affect IE or FF.
The scrollbar still seems to work (showing up when the editor content overflows).

Refs #16804, fixes #17559.
Fixes regression from b61b56813dc0c922976ca783496c374b81ca3b58.
Fixes and refactorings for Editor on Firefox.

Fixes Editor_a11y.html regression test failure and removes firefox specific code branches:

- make FF use contentEditable (like other browsers) rather than designMode
- make FF use nested <div> inside of <body> (inside of <iframe>), just like other browsers
- expand tabbing helper code (both for tabbing/shift-tabbing into and out of the iframe) to run on all browsers, not just IE
- reduce the number of branches in focus(), so that Chrome and FF use same path

Fixes #10415, #17560.
Refs #11898.
avoid spurious failure on chrome where italic button is checked,
and stop using internal editor method to position caret, refs #9460
Remove trailing whitespace from Editor value.
Fixes test failures on Chrome in Editor_mouse.html, Editor_a11y.html.
Fixes #17561.
Add test case for clearing editor then focusing it.  Refs #10268.
Remove _cursorToStart code that's apparently no longer needed.  Fixes #17568.
Add test case for setting editor value before focusing it, refs #9151.
Also removing related &nbsp code that no longer seems necessary.