Various: Validate parameters presence, type and value

Ref #251
Various: Validate CLDR content

Ref #251
Various: Validate default locale

Validate if default locale has ever been set on any static method call.

Ref #251
fix Various: Validate parameters presence, type and value

functional tests
fix Various: Validate CLDR content
fix Various: Validate default locale
README: Create Error reference section

Fixes #251