This allows caching results with --runs_per_test.

Otherwise the tests just stop once they succeed, or don't even run at
all if they passed in a previous run.

- Had to add support for files and environment variables as well.
- I can't compile on windows so I'm sure there will be some issues.
- Tested end-to-end with the simple ssl fullstack test.

I tried actually doing a build on my home desktop, and none of these
run with python 3.3, which is /usr/bin/python on my home desktop.

There may be a way to use third_party's protobuf (and this
may eventually be necessary) but I haven't yet figured out
how to do it correctly. It can happen later.

The source code is moved from src/python to
src/python/src. A setup.py is added at
src/python. The build_python.sh and
run_python.sh scripts are updated to build
and run the Python tests by building a
package and installing it in the developer's
Python 2.7 virtual environment.

Refactor the code a little to make this easier to munge around.

Run faster on smaller machines.

Don't watch '.' prefixed files for changes. These files don't typically contribute to builds, and are used as vim temp files.