Testing the released version in a local env

[kalmarek]

The first one should be run exactly as a typical user would install it:

julia -e "env = tempname(); mkpath(env); using Pkg; Pkg.activate(env); Pkg.add("Oscar"); Pkg.test("Oscar"); Pkg.test("AbstractAlgebra");  ..." 

(testing all cornerstones individually as well)
For this tests no changes to JULIA_PKG_DIR should be present. (I don't care about bandwidth:)

Most preferably a similar one which devs all the packages in a local environment should be run as well. this would have caught
oscar-system/GAP.jl#310