split in two part observations class

Author: AntSimi

src/py_eddy_tracker/featured_tracking/old_tracker_reference.py

@@ -1,4 +1,4 @@
-from ..observations import EddiesObservations as Model
+from ..observations.observation import EddiesObservations as Model
 from ..dataset.grid import RegularGridDataset
 from numpy import where, meshgrid, bincount, ones, unique, bool_, arange
 from numba import njit

src/py_eddy_tracker/observations/__init__.py

@@ -0,0 +1,3 @@
+# -*- coding: utf-8 -*-
+"""
+"""