Traits cleaning, CBT example & bug fixes (#72)

* Some cleaning, CBT example, fix mod switch and add LUT correctness test to BR test

* finished trait cleaning

* removed trait aliastoutside of backend

core/src/layouts/lwe_pt.rs

@@ -87,3 +87,9 @@ impl<D: DataMut> LWEPlaintextToMut for LWEPlaintext<D> {
         }
     }
 }
+
+impl<D: DataMut> LWEPlaintext<D> {
+    pub fn data_mut(&mut self) -> &mut VecZnx<D> {
+        &mut self.data
+    }
+}