Improved tag query allows better tag searching with + and - tag prefix

Adding support for the following tag query prefixes: '-' (exclusionary tags) or '+' (inclusionary tags)
e.g.: ?path=vacations&tags=mountains,beach,horses
        will show routes WITH 'mountains' OR 'beach' OR 'horses'

e.g.: ?path=vacations&tags=mountains,beach,+horses
        will show routes WITH ('mountains' OR 'beach')  AND 'horses'

 e.g.: ?path=vacations&tags=mountains,+beach,-horses
        will show routes WITH 'mountains' AND 'beach' AND NO 'horses'