upgrade to sbt 0.13.7

it's what the cool kids are using

safer to keep the blank lines in our *.sbt files for now though
Merge pull request #116 from NetLogo/sbt-0.13.7

upgrade to sbt 0.13.7
Update NetLogo-Headless
Revert "Disabling dependency permissioning in these pastures..."

This reverts commit 75ef923cfa8213511ed5b5bdc82c2db9ae244df9.
Getting the dependency checker running again
WIP