Added serialization

Automatically saves current batch to AppData when clicking next, previous or new, and on add-in shutdown. Also loads it again during add-in startup.
Completed Excel export and various other updates

 * Cleaned up taxon getters and setters
 * Added required methods to TaxonList
 * Overhauled Excel export functionality
 * Tracking number set from file when taxon name details updated
 * Added ribbon tools to delete current record, clear batch, or copy species details from previous record
 * Added a dictionary and class to keep track of field names and settings