EmberAPI\clsAPIHTTP Method documentation

Completed method documentation
Added additional unit test case
EmberAPI\clsAPIXML

Documented potential problem as TODO for later analysis
EmberAPI\clsAPIStringUtils and clsTrailers UT and docs

- Method documentation for both
- Unit testing for both (Strings is partial)
- Numerous corrections as a result of unit testing

frmMain was modified due to reversal/correction of logic for
StringUtils.AlphaNumericOnly