Make it possible to use a relative path in Parent_Config.
Improved error and debug logging for MultiBackend driver.
Improved logging of function parameters in exception backtrace.
Improved error and debug logging for Voyager drivers.
Relay record id to checkFunction() so that the backend can return configuration based on the record (e.g. MultiBackend driver can get config from proper backend).
Fixed error status and message reporting for restful request (leftover from VuFind 1).
Merge commit 'd9c8fa64cd7b7bc51f4ddd9d0d46ddd4dcf8dd29' into vufind-master
Merge pull request #68 from KDK-Alli/vufind-master

Assorted improvements from National Library of Finland.