piglit-merge-results.py: Drop dead code

An instance of core.Environment was being created, but never used.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
piglit-merge-results.py: Convert from getopt to argparse

Creates a smaller, simpler file that should be easier to maintain going
forward.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
piglit-summary-html.py: replace getopt with argparse

Less code, easier to read and more standard, and free help messages.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
piglit-summary-junit.py: Convert optparse to argparse

Optparse has been deprecated in favor of argparse upstream (PEP 389
http://www.python.org/dev/peps/pep-0389/), and since we are using
argparse already in the other modules, it makes sense to replace
optparse and use only one parsing method in all piglit.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>