[edoc] remove functionality related to packages

Packages have been removed trom the language. There's no need to have code supporting them.

The 'subpackages' option is left, since some projects use recursive source directories. 
I would prefer if the 'subpackages' option was renamed to 'recursive' (but keeping 'subpackages' as an undocumented alias). But this can be fixed afterwards too if you don't want to do it now.