SW-98. Able to create sdist archives from SCons.

Added commands for sdist and sdist-native targets.
Finished updates to bin/openVisualizerApp SConscript.
Added 'build' directory to repository, by adding a dummy .gitignore. Must
ensure this directory already exists because it may be created while the
user is superuser when running the UI. Superuser ownership of build means
other SCons targets, like 'docs', can write to that directory.