Log Message:
fuse-unionfs: Simplify the package a bit

- MASTER_SITE_GITHUB only needs the repository owner username, adjust it in
  DISTNAME in order to avoid DIST_SUBDIR and WRKSRC redefinition
- Add LICENSE
- Append to USE_TOOLS
- Both INSTALLATION_DIRS and pre-install target are not needed because it is
  done via Makefile (needed a little adjustements of patch-Makefile
  `install -d' of ${MANDIR})

Last item discussed with <maya> (any possible regression is mine though!)