Switched all sysdb.io links to https://
Added the SysDB homepage to all manpages.
doc: Use asciidoc instead of a2x and added asciidoc.conf. This allows to specify custom macros, which is currently used to turn references to other manpages into links in the HTML output. In general, it will make it easier to apply customizations.
documentation: Unified author information.
doc: Added documentation for all existing plugins. Added one manpage for each plugin.