River: Add reach split methods.

src/Model/Geometry/Reach.py

@@ -892,3 +892,20 @@ class Reach(SQLSubModel):
 
             profile.rk = previous.rk + dist
             previous = profile
+
+    def _split(self, profile, reach1, reach2):
+        if profile is None:
+            return
+
+        nr1 = Reach(status=self._status, parent=reach1)
+        nr2 = Reach(status=self._status, parent=reach2)
+
+        ind = self.profiles.index(profile)
+
+        nr1_profiles = self.profiles[:ind+1]
+        nr2_profiles = self.profiles[ind:]
+
+        nr1._profiles = list(map(lambda p: p.cloned_for(nr1), nr1_profiles))
+        nr2._profiles = list(map(lambda p: p.cloned_for(nr2), nr2_profiles))
+
+        return nr1, nr2