* remove set(), revert to old behavior where = resizes

* try to be clever in matrix ctors and operator=: be lazy when we can, always allow
  to copy rowvector into columnvector, check the template parameters,
  try to factor the code better
* add missing copy ctor in UnalignedType
* fix bug in the traits of DiagonalProduct
* renaming: EIGEN_TUNE_FOR_CPU_CACHE_SIZE
* update the dox a little

test/stdvector.cpp

@@ -43,7 +43,7 @@ void check_stdvector_matrix(const MatrixType& m)
   }
 
   v.resize(21);
-  v[20].set(x);
+  v[20] = x;
   VERIFY_IS_APPROX(v[20], x);
   v.resize(22,y);
   VERIFY_IS_APPROX(v[21], y);