[W.I.P.] Curve Tools plugin

[tkbd]

Progress report
The simple setting for a curve editing on Tweak mode is to assign ONLY a left click to Move.
Probably other main tweak button options are ignored.
For example Assign LMB button to Move normal,scale and radial)

And ....Most Tweak option combinations were no problem.
But an error cause on AXIS option in Tweak Palette,
The case that choose a following options either.

• Normal
  
• Element Nomal
  
• Element Nomal(Edges)
  

And try to edit for move curve elements.
Then Wings3D will crush

Code:

Dump written 2020-11-21_21-57
Version: 2.2.6.1
OS: macOS Mojave Version 10.14.6 (Build 18G6042)
GPU: Intel Inc. | Intel Iris OpenGL Engine
Window: {plugin,{curves,geom}}
Reason: {case_clause,element_normal}

Stack trace:
[{curve_tweak,do_tweak,6,[{file,"curve_tweak.erl"},{line,357}]},
{curve_tweak,do_tweak_0,6,[{file,"curve_tweak.erl"},{line,309}]},
{curve_tweak,handle_tweak_drag_event_0,2,
              [{file,"curve_tweak.erl"},{line,457}]},
{wings_wm,handle_event,3,[{file,"wings_wm.erl"},{line,1029}]},
{wings_wm,send_event,2,[{file,"wings_wm.erl"},{line,996}]},
{wings_wm,do_dispatch,2,[{file,"wings_wm.erl"},{line,888}]},
{wings_wm,get_and_dispatch,0,[{file,"wings_wm.erl"},{line,683}]},
{wings,init_part2,3,[{file,"wings.erl"},{line,108}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,249}]}]