Correct handling of long, narrow, and stand-alone weekday names

[JCEmmons]

Need to enhance the processing of available date formats, to handle cases of long, narrow, and stand-alone weekday names correctly. For example, a request for just:

{weekday: 'long'}

should return, simply "Monday" or "Thursday" in English, rather than "14 Mon".

Right now, the CLDR availableFormats contain only the pattern letter "E", and we need to expand on that so that "EEEE" ( long ), "EEEEE", narrow, or stand-alone patterns ( "ccc", "cccc", "ccccc" ) are also processed correctly.