Fix T51338: Add an offset to the internal thread, validate

Bumped version to 0.3.3
The crash was in Create_Internal_Thread_End_Verts
Possibly creating vert coord with the same values
added a small random offset to the x and y in the case
j == 0
Added a mesh.validate with a print function in case of
failures as I'm not sure that the generator will produce
valid results all the time
The print function will tell that something is wrong though
Removed a reduntant for loop - in range(1)
Small cleanup