Added Trove library for collections

[Trove](http://trove.starlight-systems.com/) is high performance collections library for Java.

In this case Trove decreases memory usage of AdAway, but increases .apk file size by about 500 KB. I have not done any performance measurements of hosts sources processing speed.

Java heap allocated at the end of ApplyService.apply() after GC, with default hosts sources:
With Java HashSet and HashMap: 8.236 MB
With Trove THashSet and THashMap: 7.328 MB

@dschuermann as you are the maintainer of AdAway, it's up to you to decide whether to move from Java native collections to Trove.