Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "Add & fix licensing in README.rst files, align ext"
  - Add & fix licensing in README.rst files, align ext

    Rename all variations of README files to README.rst.
    Fix license headers according to OPNFV Contribution Guidelines [1].

    Markdown syntax will be switched to rst in an ulterior change.

    [1] https://wiki.opnfv.org/display/DEV/Contribution+Guidelines

    Change-Id: I2c71fd62b38f218545507c79c39e07dbd35f7c88
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>