McHorse's McLib

This update features a couple of cool quality of life tweaks to different GUI elements, as well as GUI rendering optimization.

• Added an ability to use right counterpart keys for Shift, Ctrl and Alt (suggested by Silverx)
• Added separate mod option for mouse button presses
• Added mouse wheel display option to mouse button presses display option
• Added View all keyframes and Select all keyframes context menu options to keyframe elements
• Added View all keyframes (Home key) and Select all keyframes (Ctrl + A key combo, suggested by Chunk7) to keyframe elements
• Added Drop the item down and Clear the item context menu options to item slot element
• Added viewport culling to GUI system which prevents rendering of elements which are not seen on the screen
• Added Copy transformations and multiple paste contet menu options to GUI transformation editor element (3x3 grid with Translate, Scale, Rotate labels)
• Changed min and max zoom levels for keyframe elements
• Fixed (or rather reduced) multi-skin collision with other skins
• Fixed keyboard input in texture picker always selecting the last element
• Fixed texture picker resetting skin upon closing