Tweak maps interchange z-index

Allows the interchange circle to neatly sit above curves or junctions
Map CSS changes

-Deprecate catch-all terminus class
-Introduce terminus-top and terminus-bottom to replace terminus
-Tweak z-index on line
Add Piccadilly line

-Introduces line page for the Piccadilly line
-Opens bug 1 - “Heathrow Airport zone fixes”
-Clean-up:
—Opens bug 2 - “Circle line - Edgware Road”
—Opens bug 3 - “Bakerloo line - Labyrinth count”