Separate annotation from processor on AutoService

[andreaselias]

Should separate the annotation from the processor, this way we wont get the following warning and it would be prepared for gradle 5.

The following annotation processors were detected on the compile classpath: 'com.google.auto.service.processor.AutoServiceProcessor'. Detecting annotation processors on the compile classpath is deprecated and Gradle 5.0 will ignore them. Please add them to the annotation processor path instead. If you did not intend to use annotation processors, you can use the '-proc:none' compiler argument to ignore them.