C3D importer: updated property descriptions and scaling values

The minimum value for the 'scale' property has been decreased,
allowing even smaller scales (some C3D files use huge coordinates).
The effect of the 'from_inches' property has been changed to match its
description.

Reviewed by: dmbasso

Differential: D1195

io_anim_c3d/__init__.py

@@ -110,10 +110,10 @@ class C3DImporter(bpy.types.Operator):
     Y_up = BoolProperty(
             name="Up vector is Y axis",
             default=False,
-            description="Convert to Blender coordinates",
+            description="Check when the data uses Y-up, uncheck when it uses Z-up",
             )
     from_inches = BoolProperty(
-            name="Convert from inches to metric",
+            name="Convert from inches to meters",
             default=False,
             description="Scale by 2.54/100",
             )
@@ -121,7 +121,7 @@ class C3DImporter(bpy.types.Operator):
             name="Scale",
             default=1.0,
             description="Scale the positions by this value",
-            min=0.0001, max=1000000.0,
+            min=0.0000001, max=1000000.0,
             soft_min=0.001, soft_max=100.0,
             )
     auto_scale = BoolProperty(
@@ -229,7 +229,7 @@ class C3DImporter(bpy.types.Operator):
         # determine the final scale
         height = self.find_height(ms)
         #print('h', height)
-        scale = 1.0 if not self.properties.from_inches else 2.54
+        scale = 1.0 if not self.properties.from_inches else 0.0254
         scale *= ms.scale
         if self.properties.auto_magnitude:
             scale = self.adjust_scale_magnitude(height, scale)