StreetNetwork: correction for oneway street projection

if the projection is near the target of an edge, we want to start from
the target but the reversal edge might not exists(for one way street for
example). we thus forbid to start from the source.
Georef: add test
Georef: add comment in test
Merge pull request #662 from antoine-de/fix_georef_oneway

StreetNetwork: correction for oneway street projection