Removed the required field check for agency_id and route_desc as these are defined as optional in RTFS in routes.txt.
If the location type in stops.txt is unknown, don't fail, just return null. There are agency feeds out there that break this rule.
shape_pt_sequence is not a required field in trips.txt.
Delete GTFS.Test.csproj

Didn't mean to add this
Merged changes from 3 more fixes pr.
Merge branch 'pkillick-route_desc-optional'