Add cycleway:left/right=opposite_lane

Only cycleway=opposite_lane was considered, although cycleway:left (or cycleway:right) often occurs and is the recommended tag.

In the case of a street which is tagged "cycleway:left=lane" and "cycleway:right=opposite_lane", which value will be chosen for cycleway tag in obf?
It should be 'opposite_lane' (because it gives the information it is not a oneway street for bicycle), but I'm not sure it will.
Merge pull request #157 from GiZig/patch-17

Add cycleway:left/right=opposite_lane