scide + lang: Fix openDocument bug

Signed-off-by: Scott Wilson <i@scottwilson.ca>
scide + lang: Remove Document redirect

This merges the Document and ScIDEDocument classes. This should improve readability and maintainability, and simplifies the implementation. As part of this:

- some duplicate methods are deprecated
- the previous Document has been copied into the scel folder to avoid breaking EmacsDocument

Signed-off-by: Scott Wilson <i@scottwilson.ca>
Merge pull request #997 from supercollider/fixOpenDocument

Fix open document