Experimental/cuke import format

As a follow up to #717, this branch update and PR changes cucumber tests so they use .osm files by default, instead of .pbf. This makes the initial run of tests much faster, since there's no need to use osmosis to convert the .osm file to .pbf before reading by osrm.

Since most people will be using .pbf in real life, a smaller suite has been added that tests the .pbf import. It doesn't cover all routing aspects, since it's just the import itself that must be tested. But it does try to cover nodes, ways, relations and some special situations.

To fix a failing tests, a check for empty input has been added to osrm-extract.
The warning about .osm format being depreciated has been removed, since it's in fact fully supported.