using a session for basic auth (not session aware) clients for WebDAV
and GroupDAV. The "sessionid" get's constructed from the basic auth
credentials and is not random (as the clients dont store them).
--> speeds up the use of *DAV
--> stops *DAV handlers to created numerious sessions
- exceptions get now always logged to the error_log
- in the webgui it's now configurable, if the message contains a
stacktrace (incl. function arguments) - default no (security)
- command line interfaces get detected and contain no html anymore
- webdav and groupdav send the exceptions as basic auth realms to the
client
- webdav and groupdav login failures contain the reason as part of the
basic auth realm
