Add option to source configuration from a file
    
    If the configfile:// schema is used, the data is sourced from an ini
    style config file instead of being read from a database.
    
    The tables in this data source will be considered read-only and
    all modification functions will throw exceptions.
    
    Only 2 and 3 columns tables are supported, and the first column
    values must not contain spaces (typically a name/identifier).
    
    The adminconfig db is the only supported one at this time.
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>