Fixed .gitmodule for Ansible deployments

Currently, Ansible always set the --remote got git submodule update
operations.
Since no branch is specified for the submodule, it defaults to
origin/master which gives an error (there is no master branch in
elFinder (https://github.com/laclasse-com/elFinder).

This patch adds a branch name for the submodule, so deploys can run
fine. A request has been sent to the ansible ML to confirm this is an
issue on the ansible side.

Translated existing tabs to spaces
(https://github.com/erasme/guidelines)