WIP on vxPDO as PDO extension
Added license file; updated vxPDO class both with methods and comments
Adeed some more methods; reduced possibilities for injections
Further improved security against injections; reduced db specific code
to fewer methods; improved caching of metadata
Rewritten retrieval of column metadata
Stubs for a class with utility functions and for loggers added
Moved future logging functionality to new namespace
Added a method for clearing the table cache
getAlias() added to vxPDOUtil class