Inter-panel cropping method. (#810)

* Inter-panel cropping method.

* 1. Save interpanelcrop option.
2. Update readme with the the new interpanelcrop argument.
3. Add a tooltip to the inter-panel crop box.

kindlecomicconverter/common_crop.py

@@ -0,0 +1,28 @@
+def threshold_from_power(power):
+    return 240-(power*64)
+
+
+'''
+Groups close values together
+'''
+def group_close_values(vals, max_dist_tolerated):
+    groups = []
+
+    group_start = -1
+    group_end = 0
+    for i in range(len(vals)):
+        dist = vals[i] - group_end
+        if group_start == -1:
+            group_start = vals[i]
+            group_end = vals[i]
+        elif dist <= max_dist_tolerated:
+            group_end = vals[i]
+        else:
+            groups.append((group_start, group_end))
+            group_start = -1
+            group_end = -1
+            
+    if group_start != -1:
+        groups.append((group_start, group_end))
+        
+    return groups