Refactor source and table derivation for data setup

[nvkelso]

This should either move to vector-datasource directly, or be generalized away:

tilequeue/tilequeue/process.py

Lines 235 to 248 in 36fca48

	def lookup_source(source):
	result = None
	if source == 'openstreetmap.org':
	result = Source('osm', source)
	elif source == 'naturalearthdata.com':
	result = Source('ne', source)
	elif source == 'openstreetmapdata.com':
	result = Source('shp', source)
	elif source == 'whosonfirst.mapzen.com':
	result = Source('wof', source)
	elif source == 'tilezen.org':
	result = Source('shp', source)
	return result

When we added the tilezen.org source for a shapefile in vector-datasource this tilequeue code had to also be updated, which is sad. The mapping could probably be declared in the source config in vector-datasource instead.