Assets handling in stage/dist

File path resolution in jar tends to differ from the way unix
filesystems handle them.
When looking for foo//bar, unix filesystems does no difference to
foo/bar. Jar files makes a difference between both which causes trouble
between play run and play stage environments.

I tried to implement a test to make the difference clearer, but i've been unable to make sbt package test .class files along with the regular ones. I tried `test:stage` but it made no difference. If anyone has ideas for this one ...