Complete rework of global math functions and NumTraits.

* Now completely generic so all standard integer types (like char...) are supported.
** add unit test for that (integer_types).
* NumTraits does no longer inherit numeric_limits
* All math functions are now templated
* Better guard (static asserts) against using certain math functions on integer types.

doc/I00_CustomizingEigen.dox

@@ -142,10 +142,13 @@ namespace Eigen {
 template<> struct NumTraits<adtl::adouble>
 {
   typedef adtl::adouble Real;
-  typedef adtl::adouble FloatingPoint;
+  typedef adtl::adouble NonInteger;
+  typedef adtl::adouble Nested;
+
   enum {
     IsComplex = 0,
-    HasFloatingPoint = 1,
+    IsInteger = 0,
+    IsSigned,
     ReadCost = 1,
     AddCost = 1,
     MulCost = 1