Make integer regexes consistent

Use ^[+-]?[0-9]+$ for signed integers, ^[+]?[0-9]+$ for unsigned
integers, and ^[+-]?[0-9]*$ for integers that can also be empty
strings.
Replace awk with grep and cut

This removes a dependency on awk at the cost of calling an extra
external program.
Update requirements
Fix player detection in pregen.sh (again)

This slipped through the cracks in commit 1a8ad311.
Flesh out regex database documentation
Don't hardcode vinbt command

Use the output of `wickedwhich vinbt vinbt.sh` instead.