Editor::setValue can fail silently in text mode

[islemaster]

In some situations, calling Editor::setValue will have no effect.

Ran across this issue on our site with our "Start Over" feature. Repro was starting a level, switching from block mode to text mode, typing a few lines, and then clicking "Start Over."

Root cause seems to be an outdated @lastAceSeenValue. This check is not checking the current value of the editor, because it's only updated when getAceValue is called, which does not include when typing into the editor. Thus the function can mistakenly think no change is needed, when in fact it is.

Either this check should query the actual current value of the ace editor, or it might not be necessary at all - hopefully Ace swallows redundant set calls internally.

[islemaster]

Here's a simple repro:

1. Start the live-reload server and open example.html
2. Open your browser JavaScript console and run editor.setValue("foo");. This works.
3. Type "bar" into the editor so that it now reads "foobar".
4. Run editor.setValue("foo"); again. This time it has no effect. Expected: The editor text changes to "foo".