Add a TrodesPosSource table upstream of TrodesPosSelection to allow for a user to insert Trodes tracking information from RawPosition, and thus an NWB file, or from a local directory into a TrodesOfflinePos table.
The TrodesPosSource table will have a single primary key for a single entry in a part table and will allow for the position data input to be switched between RawPosition and TrodesOfflinePos