Doco: Hidden configs - you won't believe what happens next!

Covered the P's, still need to do the X and just the configs.  Work in
progress, so not linked from the index yet.
+1
Unbreak webpages
Merge branch 'master' of https://github.com/friendica/red
Give Redbasic the -styled back
Also that doesn't work anymore - prettyPhoto relic
Fix webpages.  Sycning between too many codebases...
FFS, another oops
Show tag in siteinfo.  Not useful for us, quite useful for admins.
Some more previously undocumented configs.
Moved classes from reddav.php into own files.

Finished moving classes out from include/reddav.php into own files. Also
continued with namespace for RedDAV.
Improved some docs and added some todos and fixmes.
Merge pull request #4 from friendica/master

Fast forward local hub
Merge pull request #6 from tuscanhobbit/master

Fast forward local hub
content deletion issue
fix connedit > collection > checkbox position
A fix, but I have no case to verify.

I could not find out under which conditions this is relevant and therefore have no test case, but it must be of instance RedDAV\RedFile.
cleanup of sync_locations and better logging. There was one significant code change but it is unrelated to current issues, basically if no primary was set we were setting everything as primary.
Merge https://github.com/friendica/red into pending_merge
Merge pull request #636 from dawnbreak/RedDAV

Moved classes from reddav.php into own files.
bit of cleanup of hidden_configs. This is a start - we've got hundreds more.