-Quick fix to checkpoint's behaviour

This update focuses on applying changes thanks to feedback and background peperation for the planned campaign mod:

-More enemies have been added. (Chain kills should be much more achievable now.)
-More weapons have been added to the level. (It's now worth breaking boxes.)
-More ammo has been added to the level.
-Secret exit has been modified since it's very unlikely I will be remaking the secret level any time soon.
-Midway checkpoint added to reduce frustration.

-Par time & score appropriate for Wrack has been added.

I assume this map is finished now, if I change anything it'll be thanks to feedback.

-It should now be possible to run against walls without getting stuck.
-Pushwalls go slightly further now.
-Enemies have been changed slightly (Seekers now exist in the level. Some enemies don't have their back turned to the player now.)

First release