Added subdir argument, cleaned up arg handling

Added subdir argument, cleaned up arg handling

Added the subdir argument to allow to put a treecutter site on
a deeper level than just www.example.org/ now also
www.example.org/subdir can be used.

Argument handling was changed so that sitemap gets all arguments in
its constructor as it deals the arguments at different stages.
All arguments are handed to sitemap that then distribute the needed
arguments.