support mssql query generation

This commit adds support to various parts of QDjango to generate proper
MSSQL/TSQL for qdjango use. All auto tests pass, with the exception of
using the QTime type, which appears to be broken currently in the QODBC
driver.
Merge pull request #26 from mbroadst/support-mssql

support mssql query generation
add initial test for orderLimitSql (will break CI)
fix CI