Bugs 157 and 377 - General tightening/testing of vectorwise ops:

* add lots of static assertions making it very explicit when all these ops
are supposed to work:
** all ops require the rhs vector to go in the right direction
** all ops already require that the lhs and rhs are of the same kind
(matrix vs vector) otherwise we'd have to do complex work
** multiplicative ops (introduced Kibeom's patch) are restricted to arrays, if only because for matrices they could be ambiguous.

* add a new test, vectorwiseop.cpp.

* these compound-assign operators used to be implemented with for loops:

   for(Index j=0; j<subVectors(); ++j)
     subVector(j).array() += other.derived().array();

This didn't seem to be needed; replaced by using expressions like operator+ and operator- did.

Eigen/src/Core/util/StaticAssert.h

@@ -97,7 +97,10 @@
         THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY,
         YOU_ARE_TRYING_TO_USE_AN_INDEX_BASED_ACCESSOR_ON_AN_EXPRESSION_THAT_DOES_NOT_SUPPORT_THAT,
         THIS_METHOD_IS_ONLY_FOR_1x1_EXPRESSIONS,
-        THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_OF_BOOL
+        THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_OF_BOOL,
+        THIS_METHOD_IS_ONLY_FOR_ARRAYS_NOT_MATRICES,
+        YOU_PASSED_A_ROW_VECTOR_BUT_A_COLUMN_VECTOR_WAS_EXPECTED,
+        YOU_PASSED_A_COLUMN_VECTOR_BUT_A_ROW_VECTOR_WAS_EXPECTED
       };
     };
 
@@ -197,4 +200,15 @@
       EIGEN_STATIC_ASSERT(internal::is_lvalue<Derived>::value, \
                           THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY)
 
+#define EIGEN_STATIC_ASSERT_ARRAYXPR(Derived) \
+      EIGEN_STATIC_ASSERT((internal::is_same<typename internal::traits<Derived>::XprKind, ArrayXpr>::value), \
+                          THIS_METHOD_IS_ONLY_FOR_ARRAYS_NOT_MATRICES)
+
+#define EIGEN_STATIC_ASSERT_SAME_XPR_KIND(Derived1, Derived2) \
+      EIGEN_STATIC_ASSERT((internal::is_same<typename internal::traits<Derived1>::XprKind, \
+                                             typename internal::traits<Derived2>::XprKind \
+                                            >::value), \
+                          YOU_CANNOT_MIX_ARRAYS_AND_MATRICES)
+
+
 #endif // EIGEN_STATIC_ASSERT_H