geometry changes/fixes/new features

new grid walkers + fixes
new test-cases
worked on step/and turn detection
android offline-data-reader
worked on vap-grouping

math/DrawList.h

@@ -60,6 +60,7 @@ public:
 
 	/** add a new user-element and its probability */
 	void add(T element, const double probability) {
+		Assert::isTrue(probability >= 0, "probability must not be negative!");
 		cumProbability += probability;
 		elements.push_back(Entry(element, cumProbability));
 	}