ide: Add support for getting the last selection made on a Document

Signed-off-by: Scott Wilson <i@scottwilson.ca>
ide: Add support for setting the selection of a Document in the last active editor

Signed-off-by: Scott Wilson <i@scottwilson.ca>
class library: updates for Document selection methods

Signed-off-by: Scott Wilson <i@scottwilson.ca>
ide + class lib: Add missing support for Document:editable_

Signed-off-by: Scott Wilson <i@scottwilson.ca>
ide + class lib: Add support for missing promptToSave

Signed-off-by: Scott Wilson <i@scottwilson.ca>
ide + class lib: Add support for missing Document removeUndo

Signed-off-by: Scott Wilson <i@scottwilson.ca>
ide + lang: Fix Document global key actions bug mentioned in Issue #1159

Signed-off-by: Scott Wilson <i@scottwilson.ca>
Merge pull request #1213 from supercollider/More-Document

More document stuff