Updated get-database-type-specifier to handle text/longchar type

Updated get-database-type-specifier to handle text/longchar type
and refactored

 * added a warning above defaulting to VARCHAR (since its probably NOT
   what is expected on a bad type specifier).

 * added a case where the specified type being a string, passes that
   string directly (to better/more easily allow db-specific
   data-types).

 * added cases where longchar or text converts to text, and exported
   those symbols (as this seemed type seemed to be missing from
   fddl/oddl anyway).

 * reorganized these default methods into a single method with a case
   statement rather than many eql specified methods (about half the
   code)

 * updated the docs to use text instead of longchar since text is a
   more standard db-type (pg,my,and ms all use text)