[SPARK-2924] Required by scala 2.11, only one fun/ctor amongst overriden alternatives, can have default argument(s).

...riden alternatives, can have default argument.

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

Closes #2750 from ScrapCodes/SPARK-2924/default-args-removed and squashes the following commits:

d9785c3 [Prashant Sharma] [SPARK-2924] Required by scala 2.11, only one function/ctor amongst overriden alternatives, can have default argument.