build: Add build support for relative file urls to the bnd gradle plugin
build: Add build support for relative file urls to the bnd gradle plugin

When testing using a locally built gradle plugin, we had to specify an
absolute file url. Now we can specific a relative file url and even skip
the file scheme.

Signed-off-by: BJ Hargrave <3d26bb3930946e3370762d769a073cece444c2d8@bjhargrave.com>

GEBIT/bnd,psoreide/bnd,xtracoder/bnd,lostiniceland/bnd,psoreide/bnd,mcculls/bnd,mcculls/bnd,magnet/bnd,joansmith/bnd,mcculls/bnd,joansmith/bnd,lostiniceland/bnd,magnet/bnd,magnet/bnd,xtracoder/bnd,GEBIT/bnd,psoreide/bnd,lostiniceland/bnd