Updated DDL statement generation to use quote_value from DO
Updated DDL statement generation to use quote_value from DO

* DRYs up the quoting logic in DDL generation by using the DO quoting
  method, which in some cases use the native quoting functions provided
  by the database.  This is better becaue all SELECT, UPDATE, INSERT
  statements already use these methods so they are better tested and
  more reliable than maintaining the code in dm-core.
* Removed a few special case column types where the DB engine has an
  alias to the ANSI SQL column type anyway.  This brings the query
  generation for DDL statements closer to the ANSI spec.
* Use placeholders for LIMIT and OFFSET in SELECT statements
* Updated YAML adapter to return an empty Array if it is unable to
  read *and* load the YAML file.

datamapper/dm-sqlite-adapter