Update parts.lua

add some partmenu actions from the doubleclick actions

also move icon list to a table in parts.lua (the same file that handles partmenu stuff), to avoid needing to also edit settings.lua every time I want to add a partmenu action from now on

is_turning events

nil string check

fix sprite material initialization

when the material is a pac material inside the sprite, initialization order messes up and leaves an invalid material, so waiting for the material to exist and reassign it seems to fix it

fix quick setup's edit materials option

it cleared existing submaterial assignations, which shouldn't happen

it allowed multiple submaterial edits but since it cleared the initial working table, it only really worked if using the right clickable option that doesn't close the DMenu.

the intended method is that we can surgically edit any material at any time without such troublesome workarounds as re-pasting old submaterial assignation

right click shortcut: edit sprite/particle/beam material

creates a material_2d part for it and auto-links it

Merge pull request #1416 from textstack/develop

viewer_steamid improvements

sort folders in save menu

there was another function to apply the folder sorting code to

sort outfit folders in the load/save editor menu