Northgate route nits

[nickswalker]

• Shift all Northgate route starts to station mezzanine/ped-bridge. Currently they start at street level, cross 1st ave and use the ramp to the bridge on that side (not what we ever do)
• Avoid the sketchy crossing at N Northgate Way and Ashworth Ave in https://raceconditionrunning.com/routes/northgate-bitter-lake-ob/
• Consider truncating https://raceconditionrunning.com/routes/northgate-bitter-lake-ob/ to stop at Bitter Lake for sake of having well defined end point (reduces to 6mi)