apachedex: expect apachedex options to be passed as a file

Arguments passed to apachedex are complex, they contain quotes, backslashes,
spaces and they are propagated through several levels of buildout profiles
and scripts.
Simplify all this by relying on argparse ability of passing arguments from
a file. Users of this tool are now expected to generate a config file and
specify the path of this config file as an arguments.