- if possible, replace namespace in front of element tag with the prefix used in
  the xml document
- include source line of element in error messages

catch XMLSyntaxErrors that can be thrown while parsing and just log them
in failsafe mode

add _child_construct_multiple()
- iterate over all child elements of a given parent
- compare each tag to a given tag
- raise an error or log a warning if tags don't match, else construct
  the element