Refactor MsSqlConnectionStringBuilder to remove System.Data.SqlClient dependency

[jrgcubano]

We need to change MsSqlConnectionStringBuilder "ToString" implementation so we can remove the need for System.Data.SqlClient.SqlConnectionStringBuilder and System.Data.SqlClient package.

Basic refactor idea:

Follow the same implementation as MySQLConnectionStringBuilder.

[danilobreda]

I will submit a PR for this. #395

[danilobreda]

@jrgcubano the PR is done, i am open for revision.
I think this is very important to target the 2.1.1 milestone.

I did not remove the package dependency yet (i don't know how to do it on the right way).