Add option to set eta_step size for eta omega maps

It was previously fixed to 0.25 degrees. However, the users may find
it beneficial to change this.

Smaller eta_step sizes might lead to less overlap between neighboring
peaks in the eta omega maps, for example.

Signed-off-by: Patrick Avery <patrick.avery@kitware.com>

hexrd/config/findorientations.py

@@ -223,6 +223,12 @@ def bin_frames(self):
             'find_orientations:orientation_maps:bin_frames', default=1
             )
 
+    @property
+    def eta_step(self):
+        return self._cfg.get(
+            'find_orientations:orientation_maps:eta_step', default=0.25
+            )
+
     @property
     def file(self):
         temp = self._cfg.get('find_orientations:orientation_maps:file',

hexrd/findorientations.py

@@ -567,6 +567,7 @@ def generate_eta_ome_maps(cfg, hkls=None, save=True):
     eta_ome = instrument.GenerateEtaOmeMaps(
         imsd, cfg.instrument.hedm, plane_data,
         active_hkls=active_hklIDs,
+        eta_step=cfg.find_orientations.orientation_maps.eta_step,
         threshold=cfg.find_orientations.orientation_maps.threshold,
         ome_period=ome_period)