some refactorings/fixes

worked on nav-mesh stuff
new tests

navMesh/NavMeshRandom.h

@@ -36,6 +36,8 @@ namespace NM {
 		/** ctor (const/non-const using T) */
 		template <typename T> NavMeshRandom(const std::vector<T*>& srcTriangles) : lst(nextSeed()), gen(nextSeed()) {
 
+			Assert::isFalse(srcTriangles.empty(), "no triangles given. mesh is empty");
+
 			// 1st = almost always the same number?!
 			gen(); 	gen();