Partially done major overhaul - the commits following this one will
make it more useful:
* QueryInterface API in process of being overhauled; currently mostly
  functional, but needs more work
* text <-> DBKey conversion methods removed; using SMW functions instead
* Property ID <-> label conversion methods added
* Global configuration variable for default printouts added
* Global configuration variable for default printout labels added
* Work begun on as-yet unusable RelGraphInterface class
Turn "Utils" class (collection of static methods) into a
collection of global utility functions in GlobalFunctions.php