`editor.switchTo`: node.nodeValue -> node.value
`editor.switchTo`: Remove the `setCaret` option. It makes no sense.
`editor.switchTo`: Implement `editor.restoreSelectionAfterManipulation`.
New `editor._getButtons`.
New `editor._bindFocusContentWindowToButtons`.
`editor._bindFocusContentWindowToButtons` doesn't bind to dialog-openers.
Changelog entry for #546
New `editor.focusOnDocument` & rename `._bindFocusContentWindowToButtons`

to `._bindFocusOnDocumentToButtons`.
Focus is returned to the document after dialog windows close.
Document need to mark dialog-opening buttons with a class.
Document focus handling in plugin do`s and don't`s.
Documented `wym_opens_dialog` class as a backwards-incompatible change.
Fix typo.
Fix indentation.
Made ``.editor.getButtons`` public and documented it.
Fix typo.
`editor.switchTo`: don't use `editor.restoreSelectionAfterManipulation`.
`editor.mainContainer`: Use `editor.restoreSelectionAfterManipulation`.
Merge branch 'master' into issue_546

Conflicts:
	src/wymeditor/editor/base.js
Merge pull request #546 from wymeditor/issue_546

Clicking format buttons loses selection in non-IE