Improved range formats; fixed/added tests

core/Period.php

core/Period/Range.php

core/Period/Week.php

plugins/Intl/Commands/GenerateIntl.php

plugins/Intl/lang/am.json

plugins/Intl/lang/ar.json

plugins/Intl/lang/be.json

plugins/Intl/lang/bg.json

plugins/Intl/lang/bn.json

plugins/Intl/lang/bs.json

plugins/Intl/lang/ca.json

plugins/Intl/lang/cs.json

plugins/Intl/lang/cy.json

plugins/Intl/lang/da.json

plugins/Intl/lang/de.json

plugins/Intl/lang/el.json

plugins/Intl/lang/en.json

plugins/Intl/lang/es.json

plugins/Intl/lang/et.json

plugins/Intl/lang/eu.json