Add support for built-in regex with Azure SQL DB

[ErikEJ]

fixes #156

(Pending GA of regex support in Azure SQL Database)

@roji

[ErikEJ]

Verified on my activated server with:

CREATE TABLE Emails
(
ID int,
Email nvarchar(500) CONSTRAINT CK_Email CHECK (REGEXP_LIKE (Email, '^[^@]+@[^@]+$')),
)

INSERT INTO Emails VALUES (1, 'exy')

INSERT INTO Emails VALUES (2, 'ex@y')

[ErikEJ]

@roji Thoughts?