Make all array constructors explicit (#99)

* Make all array constructors explicit

to avoid accidental implicit casts like e.g.
Vector3f v = 0;
assigning nullpointer content.

matrix/Vector.hpp

@@ -29,7 +29,7 @@ public:
     {
     }
 
-    Vector(const Type data_[M]) :
+    explicit Vector(const Type data_[M]) :
         MatrixM1(data_)
     {
     }