Revisit the handling of command line options in TARDIS Batch and Site adaters

[giffels]

As @maxfischer2781 pointed out in #349, some use-cases are not covered by the current way of handling command line options.

For example:

SubmitOptions:
    spool: null
    pool: site.somewhere.de

which is translated into -spool -pool site.somewhere.de.

As @maxfischer2781 pointed out correctly, use-cases like variadic -append and <submit-variable>=<value> for condor_submit are not supported. For example:

condor_submit -append "Foo=Bar" -append "Test=Test" submit_var=123

So, the idea is to change the handling of command line options to be a list or even string of command line options in the config.

[maxfischer2781]

If we assume that people use the configuration right, we can easily support multiple styles side-by-side. Since all options correspond to clearly different data types (currently dict, plus list and str) the code can separate them cleanly. This would also allow to deprecate the old style gracefully if we want to.