Add first bits of actual functionality.

This commit includes several things:

o Remove the fake map.
o Turn loading/saving into TODOs.
o Add class MessageEditor.
  It uses the MessagesModel of the Project.
o Add a MessageEditor to MainWindow.
o Re-create MainWindow to only include minimal functionality.
o Add support for adding PositionData messages.
o Change version to "1.0 Beta"

Still no FieldEditor, but that will come.