clean up and refactor half-baked development commits and squash them into a new version.

Changes:

* support for multiple GTFS feeds as input in filtering, read default global and local configuration files
* be a bit more memory conservative
* make caching optional
* dont delete orphan edge if it would transform a degree 3 node with a possible full turn into a degree 2 node eligible for contraction
* dedicated filters for funicular and gondola
* make max snap level option more intuitive
* allow filter rules for level 0
* additional fallback for station snapping
* dont try to route for MOT unequal to trip in -T mode, force-snap to orphaned OSM station if not snap was possible
* write bounds to filtered osm
* remove unused surrounding heuristic
* use bus lanes info
* be a bit more tolerant for bus oneway streets
* create missing directories
* error if no cfg is present, clean up evaluation Makefile

src/util/Nullable.h

@@ -26,7 +26,7 @@ class Nullable {
    : val(other.val), null(other.isNull()) {}
 
   Nullable& operator=(const Nullable& other) {
-    val = other.get();
+    if (!other.isNull()) val = other.get();
     null = other.isNull();
     return *this;
   }