add support for secrets files

[matthias-kloeckner]

this introduces new env variables for user name, password and uri. more importantly user name and password can also be read from files - this is needed to securely pass secrets to the docker container by just mounting these files.

new variables:
DATA_SOURCE_USER
DATA_SOURCE_USER_FILE
DATA_SOURCE_PASS
DATA_SOURCE_PASS_FILE
DATA_SOURCE_URI

[coveralls]

Coverage decreased (-2.2%) to 49.605% when pulling fe42532 on matthias-kloeckner:master into c4f701e on wrouesnel:master.

[coveralls]

Coverage decreased (-2.2%) to 49.605% when pulling fe42532 on matthias-kloeckner:master into c4f701e on wrouesnel:master.

[coveralls]

Coverage decreased (-2.2%) to 49.605% when pulling b302718 on matthias-kloeckner:master into 1fa394d on wrouesnel:master.

[coveralls]

Coverage decreased (-2.1%) to 48.694% when pulling 8a7daeb on matthias-kloeckner:master into 81194c9 on wrouesnel:master.

[wrouesnel]

This is a sufficient change that we really need an explicit test case which proves the "win" conditions.

[coveralls]

Coverage decreased (-2.1%) to 48.694% when pulling ac60ce9 on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[hartmut-pq]

+1 would like to see secrets supported, too!

[coveralls]

Coverage decreased (-2.0%) to 48.844% when pulling abc018e on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[coveralls]

Coverage decreased (-2.0%) to 48.844% when pulling 551af02 on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[coveralls]

Coverage decreased (-2.0%) to 48.844% when pulling 97518a2 on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[coveralls]

Coverage decreased (-2.0%) to 48.844% when pulling 9328047 on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[coveralls]

Coverage decreased (-2.0%) to 48.844% when pulling c3ff253 on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[coveralls]

Coverage increased (+1.6%) to 52.388% when pulling 908912d on matthias-kloeckner:master into 1afbd62 on wrouesnel:master.

[matthias-kloeckner]

added some tests and fixed the makefile. sorry for the amount of commits - I needed some test runs on travis to understand the real problem.

[coveralls]

Coverage increased (+1.8%) to 54.135% when pulling 05f70bb on matthias-kloeckner:master into e701b80 on wrouesnel:master.

[matthias-kloeckner]

@wrouesnel
anything still missing here?

[wrouesnel]

No this is looking good. I'll give it a closer inspection tonight and merge it hopefully.