Move selection related operations into the new SelectionController.js
Merge pull request #277 from kevinlli/refactor

Move selection related operations into the new SelectionController.js
Fix TextSerializer to skip inline roots (like annotations)
Drop broken creation of a text/html version for the clipboard for now
Put custom data into drag handler instead of built-in nodes text extraction, concentrate mimedata export in new gui.MimeDataExporter
No longer needed to pass focus explicitely back for IE in synchronizeWindowSelection