Adds Baystation's Cortical borers [PORT]

Add's the Cortical borers (simplified to "Cortex borers") to /TG/station code
When I first heard about them I was intrigued and though we may wan't the feature.
I know Baystation's copyright rules allow me to do this but I also went ahead and asked for permission.
(However that may not be required due to the aforementioned copyright rules)

These are small player controlled mobs that can enter and ride in, or control any /mob/living/carbon 
They have verbs to supply their host with certain reagents, They have a vent crawl verb and a hide verb.
They work off of the "BE_ALIEN" preference setting.

Modifications by me:
- Made it work with /TG/ Code
- Added some checks using the provided procs so that weird shit doesn't happen
- Added an Event for it.

List of things prevented:
- People with Borer's being Mind transferred
- Borer changelings becoming lesser form (This was causing issues)
- Alien drones becoming queens while having a borer (This made the control irreversible)


I have noted all changes I have made in the file so that Support for issues with those changed sections can come to me and not Baystation.