Improvements

[okybaca]

documentation improvements:

• included yacy packs to doc index
• recovered old wiki article export import for later editing reflecting the recent changes
• added a advanced search parameters page from oldwiki
• added host config option introduced in yacy/yacy_search_server@055a2ea
• extended the contribution guide
• tiny fixes such as linux dowload url (1.940)

[okybaca]

@Orbiter , could you merge, please?
you can also close #6, which had been already fixed before.
thanks!

[okybaca]

great, thanks!

[okybaca]

thanks for the merge, but still, the changes are not visible at https://yacy.net/docs/.
is there some auto-publish or it must be done by hand?