Stripped trailing whitespace from sculpttrimCurve.py and reformatted it,
guided by PEP 8 and PEP 257.
Refactored world2local function to simplify the calculation.

Clarified the function's intent by using Blender's higher-level
functions and by adding detail to the docstring.
Corrected Add-on category.
Panel class:
* Renamed class to reflect purpose (initialize -> TrimCurvesPanel).

* Panel's poll function:
  * renamed self-reference variable (self -> cls) to reflect the use of
    a class method;
  * corrected result ('or' used incorrectly), and included Edit as a
    valid context.
Spaced out the panel's draw function to reflect row divisions.
Moved property definitions from the panel class to the operator class.
The properties belong to the operator, so it should define them; the
panel should merely display and update them.

Register operator before panel; unregister classes in reverse order.
Reworked panel:
* Only shows up if there is at least one mesh object in the scene;
* All items have tooltips;
* Cleaned up dropdown lists;
* Rearranged to group Curve options;
* Added separators to improve spacing of option groups.
Python's math module is no longer required.
Replaced numeric EnumProperty values with descriptive names.
DRY: repeated code blocks that deselect, select, and activate objects
replaced with a helper function (select_exclusively_and_activate).
Started breaking execute function into subfunctions.
Reworked section that aligns the curve with the view.
Added "bpy." for consistency (though unnecessary) in selection function.