Add MSSQL handling for dao query

[lsetiawan]

Overview

This PR addresses #157. Dao now can handle mssql when querying.

[emiliom]

In the test for database (engine) name, like this:

if self.engine.name is 'postgresql' or self.engine.name is 'mssql':

why are you using the is operator rather than ==? The is operator is intended for comparisons to other object literals. A string comparison should use ==. Assuming self.engine.name returns a simple string literal, the if test can then be made a bit more compact and readable:

if self.engine.name in ('postgresql', 'mssql'):

Obviously this is not a critical issue! But it was bugging me a bit ...