LessImportStatementResolver2: First version working for validation.
Fix error messages.
Fix resource loading.
Fix URI resolution.
Clean up.
Simplify error reporting for cycles.
End to plug LessImportStatementResolver2.
LessImportStatementResolver2 -> LessImportStatementResolver
LessImportStatementResolver2 -> LessImportStatementResolver
Simplify LoadOnDemandResourceDescriptions initialization.
Fix handling of absolute/relative URIs.