Add support for SELECT TOP construct for mssql dialect for limit

[christiaanwesterbeek]

MSSQL is the only dialect supported by node-sql-query that constructs a limit as

SELECT TOP [n rows] columns
FROM tablename
ORDER BY key ASC

instead of

SELECT columns
FROM tablename
ORDER BY key ASC
LIMIT n

This commit adds support for mssql and the limit property.

[christiaanwesterbeek]

@dresende Easy merge waiting (tests were added and passing)

[dresende]

Thank you