Show a situation where the decision table has 'invalid' and 'missing' rows

.. and makes a poor choice as to which one to consider 'missing' or 'invalid'.
Looks like it treats the first column as special - doesn't seem like a good
idea to me.
Merge branch 'master' into query_table

Conflicts:
	FitNesseRoot/FitNesse/UserGuide/WritingAcceptanceTests/SliM/QueryTable/content.txt
Failing unit test for query table matching #380
Improve matching invalid rows in query tables #380
Merge pull request #436 from raboof/query_table

Improving matching invalid rows in query tables #380