Closed Alpha v0.5.2

There are a ton of fixes and a couple features in this update.

Features:
!!! Initial Linux support

• Allow colour correction UI to be opened without tools mode
• Added SetSpeed input to trigger_push
• Added experimental Volumetric Lighting for env_projectedtextures
• Added Max Bounce option to energy pellet launchers

Fixes:
!!! Fixed demo player
!!! Fixed incorrect sprite scaling
!!! Fixed numerous issues with vphysics save/load causing constraints to break

• Fixed fizzling a laser reflecting cube crashing the game
• Fixed loading a save in a workshop map kicking you to the menu
• Fixed laser collision breaking after redirection
• Fixed broken shadows on underwater objects lit by a projected texture
• Fixed broken wind in SP
• Fixed broken laser colour on lasers marked as lethal
• Fixed laser end particles persisting after deactivation
• Fixed Challenge Mode end screen
• Fixed the second player viewmodel not rendering in splitscreen
• Fixed the vertical reportaling exploit not working
• Fixed snapping of personality core animations
• Fixed portal ghosts showing inconsistently
• Fixed Schrodinger Cube linkage breaking after save/load
• Fixed player view transitions on angled portals
• Fixed paint not painting anything on Linux
• Fixed portal gun recoil damping
• Fixed chapters not being unlocked
• Fixed env_projectedtexture min/max being incorrectly clamped
• Fixed gel splash screen effect
• Fixed trigger_paint_cleanser ignoring spawnflags
• Fixed incorrect panel rotation in sp_a2_bts5
• Fixed tracktrain parenting causing issues with Wheatley in sp_a2_core
• Fixed subtitle colouring
• Fixed voice line pitch
• Fixed VGUI screens not rendering when looking at them sometimes
• Fixed point_posecontroller drift
• Fixed fizzler sounds sometimes always playing