Change desktop logger to Logback

[Avalancs]

Description

Work in progress, do not merge! This is a prototype for #416. I got the Engine tests and desktop to work with SLF4J and Logback, but I do not know how to download the android part.

Testing

1. Run JUnit tests from the Engine directory. They do not log anything, but you should not receive an exception from SLF4J about missing logger
2. Start the game with the "run" task, and see if messages are printed to console

Outstanding Work

• [ ] Download android, copy logback.xml to src/main/resource/assets/logback.xml
• [ ] Replace ConsoleAppender with ch.qos.logback.classic.android.LogcatAppender inside the copied logback.xml
• [ ] Change build.gradle to use

runtime group: 'com.github.tony19', name: 'logback-android', version: '2.0.0'
runtime group: 'com.github.tony19', name: 'logback-android-classic', version: '1.1.1-6'

instead of ch.qos.logback.

• [ ] Test if logging works when the game is started (it might output an error, or just simply doesn't paste any text. See http://logback.qos.ch/manual/configuration.html#automaticStatusPrinting for help with debugging the logging configuration

[GooeyHub]

Hooray Jenkins reported success with all tests good!