Adds more details to INSTALL.md
Adds more details to INSTALL.md

Adds a little more details to the INSTALL.md file, mostly related to the vagrant setup
Turbo87/skylines,skylines-project/skylines,Harry-R/skylines,Harry-R/skylines,dkm/skylines,RBE-Avionik/skylines,snip/skylines,TobiasLohner/SkyLines,RBE-Avionik/skylines,skylines-project/skylines,Turbo87/skylines,skylines-project/skylines,skylines-project/skylines,Harry-R/skylines,shadowoneau/skylines,RBE-Avionik/skylines,kerel-fs/skylines,shadowoneau/skylines,dkm/skylines,shadowoneau/skylines,Harry-R/skylines,TobiasLohner/SkyLines,kerel-fs/skylines,TobiasLohner/SkyLines,snip/skylines,Turbo87/skylines,snip/skylines,RBE-Avionik/skylines,dkm/skylines,Turbo87/skylines,dkm/skylines,shadowoneau/skylines,kerel-fs/skylines