Don't mark document as modified when ctrl-space is pressed

modified:   src/extensions/default/JavaScriptCodeHints/ScopeManager.jsDon't update the modified range when 'null' keys (ctrl-space) are hinted.

modified:   src/extensions/default/JavaScriptCodeHints/main.js
When changing files, reset documentChanges to null.

modified:   src/extensions/default/JavaScriptCodeHints/unittests.js
Restore that content of a file after each test.
Update a test to wait for hints after it asks for hints. If the hints are not waited for the editor will be torn down before the hint completes, causing a null pointer exception.