[SPARK-2069] MIMA false positives

Fixes SPARK 2070 and 2071

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #1021 from ScrapCodes/SPARK-2070/package-private-methods and squashes the following commits:

7979a57 [Prashant Sharma] addressed code review comments
558546d [Prashant Sharma] A little fancy error message.
59275ab [Prashant Sharma] SPARK-2071 Mima ignores classes and its members from previous versions too.
0c4ff2b [Prashant Sharma] SPARK-2070 Ignore methods along with annotated classes.