Don't use System.out.println() and Throwable.printStackTrace()

Summary: Printing to stdout is a really bad practice. Use logging which can be configured by the users of Selendroid as needed, e.g. hidden from the console and redirected to a file.

Test Plan:
  $ mvn clean install
  ...
  [INFO] ------------------------------------------------------------------------
  [INFO] Reactor Summary:
  [INFO]
  [INFO] selendroid ........................................ SUCCESS [0.137s]
  [INFO] android-driver-app ................................ SUCCESS [2.024s]
  [INFO] selendroid-server-common .......................... SUCCESS [1.013s]
  [INFO] selendroid-server ................................. SUCCESS [17.088s]
  [INFO] selendroid-grid-plugin ............................ SUCCESS [0.676s]
  [INFO] selendroid-common ................................. SUCCESS [0.914s]
  [INFO] selendroid-standalone ............................. SUCCESS [17.732s]
  [INFO] selendroid-client ................................. SUCCESS [0.633s]
  [INFO] selendroid-test-app ............................... SUCCESS [4.871s]
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD SUCCESS
  [INFO] ------------------------------------------------------------------------

Reviewers: ainsej, kumar.rangarajan, juyuan.yang.9, asm

Reviewed By: asm

Differential Revision: https://reviews.facebook.net/D28887