Fixed small inconsistencies in URLs.

Fixed small inconsistencies in URLs. Left workflow link as-is.

Fixed some small inconsistencies in URLs and updated all disfunctional links. Note, you may want to update the link for the database setup guide to [a newer version of Ubuntu](https://wiki.ubuntu.com/Releases).

Fixed some small inconsistencies in URLs and simplified reference links which are only called once.

Alternatively, you may use the tile usage policy link between the parentheses instead of the tiles 'link'.
"`OSMF tileservers ([Tile Usage Policy](https://operations.osmfoundation.org/policies/tiles/))`"

For Mapnik (XML) stylesheets, also the link "`[Community list of Mapnik stylesheets](https://github.com/mapnik/mapnik/wiki/StyleShare)`" could be added.
( from https://wiki.openstreetmap.org/wiki/Stylesheets )

Permalink for mapnik-stylesheets template line, just fyi (the existing link with `master` seems fine).
https://github.com/openstreetmap/mapnik-stylesheets/blob/236f8d0ab17b792300679cedf9afa5b0feab301b/inc/settings.xml.inc.template#L16