Add timings

This addresses [REEF-28]: Timings are added to the various important event
handlers using the recently added `LogScope` classes.

The code was written by Julia Wang <Qiuhe.Wang@microsoft.com>

Closes #12
REEF-36: Add Apache RAT
  * Added RAT
  * Added license headers to poms
  * Removed eclipse plugin for which no license was available
  * Added a missing licensing header in the .proto files
  * Added a missing licensing header in the .avsc files