Dev/rosenblatttransform (#241)

- added rosenblatttransform 
- added 3x3 eta methods 
- interpolation can be used with various eta functions
- added documentation for interpolation, eta calculation 
- exposed full eta struct in python 
- disable ClusterFinder for 2x2 clusters 
- factory function for ClusterVector

---------

Co-authored-by: Dhanya Thattil <dhanya.thattil@psi.ch>
Co-authored-by: Erik Fröjdh <erik.frojdh@psi.ch>

python/src/bind_Cluster.hpp

@@ -80,9 +80,7 @@ void reduce_to_3x3(py::module &m) {
         [](const Cluster<T, ClusterSizeX, ClusterSizeY, CoordType> &cl) {
             return reduce_to_3x3(cl);
         },
-        py::return_value_policy::move,
-        "Reduce cluster to 3x3 subcluster by taking the 3x3 subcluster with "
-        "the highest photon energy.");
+        py::return_value_policy::move, R"(Reduce cluster to 3x3 subcluster)");
 }
 
 template <typename T, uint8_t ClusterSizeX, uint8_t ClusterSizeY,
@@ -95,8 +93,15 @@ void reduce_to_2x2(py::module &m) {
             return reduce_to_2x2(cl);
         },
         py::return_value_policy::move,
-        "Reduce cluster to 2x2 subcluster by taking the 2x2 subcluster with "
-        "the highest photon energy.");
+        R"(
+        Reduce cluster to 2x2 subcluster by taking the 2x2 subcluster with 
+        the highest photon energy.
+
+        RETURN: 
+        
+        reduced cluster (cluster is filled in row major ordering starting at the top left. Thus for a max subcluster in the top left corner the photon hit is at the fourth position.)
+        
+        )");
 }
 
 #pragma GCC diagnostic pop