fixes #317: bnd should generate errors on inconsistent @Reference usage
http://github.com/bndtools/bnd/issues/issue/317
Project: restore API that is used by bndtools

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
Added R5 index generation to the build
Fix build
Really fix build (sigh)
Implemented SHA checking of cached remote files
Merge remote-tracking branch 'origin/master' into next
Made some changes to the API to make it more useful