Alpha 5 - Next Section

Hey everyone! This update adds the next section, and all the functionality needed for it. Details:

Altered post processing (again)

Fixed oxygen problems:
    Fixed that oxygen wouldn't save
    Fixed that the game wouldn't save if oxygen was enabled

Made player go back to a checkpoint when oxygen reached 0
Made oxygen text go red when under 20%
Made beeping happen when oxygen goes under 20%
Changed how oxygen rounds to display

Added new section (always)

Added custom mouse cursor

Added new sounds:
    Airlock
    Breathing
    Beeping

Implemented new sounds

Added new debug commands:
    update_text
    save <type> <name> <value>