Splits EXTDocument into EXTDocument (model controller) and EXTDocumentWindowController (presentation controller).
Implements -[EXTDocumentWindowController setPageInView:].
Now that we have EXTSpectralSequence, replaces EXTViewDataSource with EXTView.sseq.
Cleans up some header files.
Merge pull request #5 from bavarious/windowcontroller

Splits EXTDocument into EXTDocument (model controller) and EXTDocumentWindowController (presentation controller)