Better Lua sandboxing and vertical scroll fix

Retro Sketch - Pixel Art & Animation

Retro Sketch makes it easy to create awesome pixel art drawings and animations.

[h2]Features[/h2] [olist] [*] Lua code is now partially sandboxed so that the app is it's own context [*] Added "Hot Reload Plugins" in settings to force reload from file each time it opens [*] Added rs_execute in Lua to allow for better control over history undo/redo [/olist] [h2]Fixes[/h2] [list] [*] Fixed an issue with vertical scroll boxes not working properly [*] Fixed an issue with vertical scroll boxes scrolling too slowly [/list]