Cleaned up some code, implemented sender colors

app/src/main/java/de/kuschku/libquassel/Client.java

...rc/main/java/de/kuschku/quasseldroid_ng/MainActivity.java

...in/java/de/kuschku/quasseldroid_ng/NetworkDrawerItem.java

app/src/main/java/de/kuschku/util/IrcUserUtils.java

app/src/main/java/de/kuschku/util/ReflectionUtils.java

app/src/main/java/de/kuschku/util/SortedListWrapper.java

app/src/main/java/de/kuschku/util/backports/Absent.java

...c/main/java/de/kuschku/util/backports/BinaryFunction.java

app/src/main/java/de/kuschku/util/backports/Consumer.java

app/src/main/java/de/kuschku/util/backports/ICollector.java

app/src/main/java/de/kuschku/util/backports/Optional.java

app/src/main/java/de/kuschku/util/backports/Optionals.java

app/src/main/java/de/kuschku/util/backports/Present.java

app/src/main/java/de/kuschku/util/backports/Stream.java

...java/de/kuschku/util/backports/collectors/Collectors.java

...a/de/kuschku/util/backports/collectors/ListCollector.java

...va/de/kuschku/util/backports/collectors/MapCollector.java