Replace testBinDir with pep8 compliant TEST_BIN_DIR

This is really a constant, not just a variable, since changing it will
cause undefined behavior. Beyond that lower cammelCase is not allowed
for variable names in pep8, so this should be changed.

This was implemented with the following command:
find . -name '*.py' | xargs -n sed -i -e 's!testBinDir!TEST_BIN_DIR!g'
find . -name '*.tests' | xargs -n sed -i -e 's!testBinDir!TEST_BIN_DIR!g'

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
framework.environment.py: Replace Environment.collectData static method

First, static methods are ugly, and python's namespaces make them even
less interesting, since a toplevel function is like a static method but
without being part of a class. Second this static method was even worse
since it had nothing to do with the class it was attached.

This is replaced with a toplevel function in the environment module.
This also removed the need for checking what OS piglit is running on,
since it blindly attempts to run all of the possible commands that we
might want using a try/except block to skip the ones that are not
returned.

V2: - Return and iterator from Environment.get_environment() instead of
      a list. This should be more efficient if we add more binaries.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
environment.py: replace loops in constructor with comprehensions

The list comprehensions are easier to read.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
environment.py: replace docstring with block comment

This was incorrectly formatted and should have been using block comments
from the beginning.

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

This patch adds docstrings to the remaining places that are needed.

V3: - spell checking

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
environment_tests.py: Add a few tests for envornment

These tests are pretty simple, but would have revealed this bug:
https://bugs.freedesktop.org/show_bug.cgi?id=71822

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