Make minidns Android agnostic

I've made minidns Android agnostic in preparation to provide this library as alternative for DNS SRV resolving in Smack and aSmack.

I prepared `build.gradle` for maven central deployment. All you need is create the `de.measite` group on OSS sonatype and create `gradle.properties` in minidns root file with a content like:
```
signing.keyId=0x78548E35
signing.secretKeyRingFile=/home/flo/.gnupg/secring.gpg
```
and `~/.gradle/gradle.properties` with
```
sonatypeUsername=username
sonatypePassword=iwonttellyou
```