Add functional tests for sqlcmd (verify all types of public and SAS URLs work well in --using)

[apoorvdeshmukh]

As a follow up to #299 we should add functional tests for scenarios such as verifying that all types of public and SAS URLs work well for specifying .bak files

[apoorvdeshmukh]

Follow up item based on comment:
Change getDbNameAsIdentifier to something more generic which is encoding the SQL statements and then move these helper functions to internal.