fix logging

[jcharlet]

Issue

The logging is broken and shows this kind of logs when starting the app or running some unit tests.

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

Another type of log was mentioned at startup stating "Starting service Pronom[...]"

Context

Introduced in PR #352 on commit ccd5a6c while fixing dependency check issues.

Fix

• put back log4j slf4j binding dependency in all modules ran or having unit tests
• tell apache.cxf to use slf4j instead of log4j (was using log4j1 and ignoring log4j2 config)
• set root logger to warn (since it's overridden on tna logs to INFO or whatever the user asks)

Acceptance tests

on unit tests

• run mvn install
• check above logs do not appear anymore

while running droid apps

• GUI
  just start the GUI
• CLI
  ./droid.sh -h is enough