Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Add license headers where missing

    While at it, compact 'set' into bash shebang where possible and
    add `make patches-copyright` target to simplify adding patch
    license headers.

    Change-Id: I0c841de72e5709e5eef915a52c5ec4a7fc0f7c37
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index a75af3d..644e5fd 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit a75af3d4c30af050dd15c0f875142f6328874fe4
+Subproject commit 644e5fdfa2f49b988a5150e2a4eefc12daecd845