fix!(eoBit): defaults to char for scalar type

Since STL's vector of bool is not a vector of bool, `swap`ing bool elements in an eoBit can lead to errors.
Using `char` is a saner default.

Potential BREAKING CHANGE.

mo/test/t-moNKlandscapesIncrEval.cpp

@@ -56,7 +56,7 @@ int main() {
   nkLandscapesEval<Solution> eval(N, K);
 
   // init
-  eoUniformGenerator<bool> uGen;
+  eoUniformGenerator<char> uGen;
   eoInitFixedLength<Solution> init(N, uGen);
 
   // verif constructor