Settings page

#46 

Added settings page with tables to showcase:
- Districts
- Zip Codes
- Parties

Also added edit/delete functions for all of these (districts has no edit functionality)

Also added Zipcode Lookups on Add/Edit user pages that will automatically assign them to their designated district #

Also created an upload script that will allow people to upload a csv of zip codes vs. district numbers so that they don't have to do it manually