Added item_creation behavior for xmlfilecontent and textfilecontent54 per #315 and #316

[vanderpol]

Added item_creation behavior, similar to new behavior in ntuser test which allows content authors to control when an item is created, and prevent false negatives when text/xml file may not contain the data required to populate an item, and would be overlooked.

[solind]

@vanderpol I need to do some research on whether the default expected behavior isn't already the "filepath_exists" behavior.

[solind]

Hi @vanderpol, thinking about this some more, I think I'm too far removed from the weeds to say for sure at this point whether an OVAL 5.11 interpreter is supposed to make an item if the file exists but the pattern or XPath does not. It certainly could do so, in which case the EntityStateSimpleBaseType check_existence operator becomes impactful on the evaluation. This is important in determining which behavior we should make the default.

@A-Biggs, can you tell us what Joval does in these cases for textfilecontent and xmlfilecontent objects?