Format of values in IDS

[CBenghi]

A few test cases state that Booleans must be specified as uppercase strings.

IDS/Documentation/testcases/scripts.md

Lines 217 to 242 in d484120

	### Booleans must be specified as uppercase strings 1/3
	``` ids attribute/fail-booleans_must_be_specified_as_uppercase_strings_1_3.ids
	Booleans must be specified as uppercase strings 1/3
	Entity: ''IFCTASK''
	Requirements:
	Attribute: ''IsMilestone'',''TRUE''
	```
	### Booleans must be specified as uppercase strings 2/3
	``` ids attribute/fail-booleans_must_be_specified_as_uppercase_strings_2_3.ids
	Booleans must be specified as uppercase strings 2/3
	Entity: ''IFCTASK''
	Requirements:
	Attribute: ''IsMilestone'',''False''
	```
	### Booleans must be specified as uppercase strings 2/3
	``` ids attribute/pass-booleans_must_be_specified_as_uppercase_strings_2_3.ids
	Booleans must be specified as uppercase strings 2/3
	Entity: ''IFCTASK''
	Requirements:
	Attribute: ''IsMilestone'',''FALSE''
	```

I think this is unreasonable.

If the whole point of using xml's xs:restriction in IDS is to allow implementers to use an existing XML library for parts of the testing, surely we must comply with the XML approach for the storage of values.

In the case of Boolean, according to xml official documentation this means that:

An instance of a datatype that is defined as boolean can have the following legal literals {true, false, 1, 0}.

This should be verified across all XML base types.

[CBenghi]

Closed with #292