Add real integration test

[dadoonet]

We should provide a simple script which does something like:

# Install and starts elasticsearch (we can get it from the .m2 dir probably)

mkdir ~/.fscrawler
mkdir /tmp/es
echo "test a file" > /tmp/es/test.txt
unzip target/fscrawler-*-SNAPSHOT.zip
cd fscrawler-*-SNAPSHOT
# TODO Write the job file here like echo "{ ... }" > ~/.fscrawler/test/_settings.json
bin/fscrawler test -loop 1
# Check the output

[dadoonet]

To do this, I'd like to provide OOTB a FSCrawler Docker image which can be used by our users but also in the context of real IT. See #586