Declare inputs and outputs in code-generation tasks
Declare inputs and outputs in code-generation tasks

This makes such tasks work with Gradle's incremental build.

In practice this change is not very useful:
- The Dagger annotation processor version we use is not fully
  compatible with Gradle incremental build, and currently causes
  unnecessary rebuild in the util package, and forces tests to always run.
  Will try the latest version later, which claims to support incremental
  build.
- AppEngine deploy task leaves behind non-writable tools.jar files.
  Reruns of any builds that include :services:*:explodeWar would fail,
  and the easiest work-around right now is to run Gradle clean task.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=232929552

google/nomulus,google/nomulus,google/nomulus,google/nomulus,google/nomulus,google/nomulus