[3.1.0] Continue building up validation functions

- Remove incorrect parsing of value aliases
- Implement most allowed and value alias checks
- Add assertIsBool, assertIsArray and assertIsLookup to ValidatorAtom
- Publish string types in VarParser

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1647 48356398-32a2-884e-a903-53898d9a118a

tests/HTMLPurifier/ConfigSchema/Validator/directive/allowedIsString.vtest

@@ -0,0 +1,10 @@
+ERROR: Value 3 in allowed in directive 'Ns.Dir' must be a string
+----
+Ns
+DESCRIPTION: Generic namespace.
+----
+ID: Ns.Dir
+TYPE: string
+DESCRIPTION: Description
+DEFAULT: 'asdf'
+ALLOWED: 'asdf', 3