Make case list export destination configurable

Make case list export destination configurable

Added command line parameter --deqp-caselist-export-file for
defining the test case list target file template.

Added new run mode, stdout-caselist, for writing all the test
cases into the stdout.

Split XML export into file handling and XML writing parts
for clarity. Renamed export utility functions to show
that multiple files are potentially created during
export.

Bug: 20890217

Change-Id: Ib6247283824203644a9953391588f1c60347405b