Add examples for IfcLogical that show proper syntax for IFC files

[AngelVelezSosa]

Problem
IfcLogical is described as being TRUE, FALSE, or UNKNOWN but all IFC files write out those values as .T.,.F. and .U. There doesn't seem to be any documentation that this is the correct method. Can we add explicit examples that show that this is correct (or not...)

Solution(s)
Valid IFC file samples that contain IfcLogical and ifcBoolean properties in all possible states.

Require schema changes?
✓ no

Require documentation changes?
✓ yes

Rule required
Need for a formal rule? Describe it
✓ normative check: every IFC file must pass this check

A clear and concise description of the rule
Check the the value of IFCBOOLEAN and IFCLOGICAL properties, make sure they are .T./.F./$ or .T./.F./.U./$ only.

Additional context

[aothms]

fyi the relevant sections from 10303-21, so the observation is correct ($ only in case of optional):

12.1.1.3 Boolean

...

The EXPRESS data type BOOLEAN shall be treated as a predefined enumerated data type with a value encoded by the graphic characters "T" or "F". These values shall correspond to true and false respectively.

12.1.1.4 Logical

...

The EXPRESS data type LOGICAL shall be treated as a predefined enumerated data type with a value encoded by the graphic characters "T", "F" or "U". These values shall correspond to true, false, and unknown respectively.