Fix Gael reports (except documention)

- "Scalar angle(int) const"  should be  "const Vector& angles() const"
- then method "coeffs" could be removed.
- avoid one letter names like h, p, r -> use alpha(), beta(), gamma() ;)
- about the "fromRotation" methods:
 - replace the ones which are not static by operator= (as in Quaternion)
 - the others are actually static methods: use a capital F: FromRotation
- method "invert" should be removed.
- use a macro to define both float and double EulerAnglesXYZ* typedefs
- AddConstIf -> not used
- no needs for NegateIfXor, compilers are extremely good at optimizing away branches based on compile time constants:
  if(IsHeadingOpposite-=IsEven) res.alpha() = -res.alpha();

unsupported/Eigen/EulerAngles

@@ -16,13 +16,19 @@
 
 #include "Eigen/src/Core/util/DisableStupidWarnings.h"
 
+namespace Eigen {
+
 /**
- *  \defgroup EulerAngles_Module EulerAngles module
- *
- *
- *
- *
- */
+  * \defgroup EulerAngles_Module EulerAngles module
+  * \brief This module provides generic euler angles rotation.
+  *
+  * \code
+  * #include <unsupported/Eigen/EulerAngles>
+  * \endcode
+  *
+  */
+
+}
 
 #include "src/EulerAngles/EulerSystem.h"
 #include "src/EulerAngles/EulerAngles.h"