Upgrade MS SQL driver

[chalkos]

The driver being used is sqljdbc4, version 4.0 which is not able to connect to MS SQL databases using windows integrated login (see #336).

According to this support & compatibility matrix, support for the version being used stopped on March 6, 2017.

Also according to the same matrix, the appropriate version to use is 6.2, since it is the most recent version that is compatible with all systems that 4.0 supported (e.g. version 6.4 drops support for SQL Server 2008), and is compatible with Java 7. As a bonus, using version 6.2 will (theoretically) add support for SQL Server 2017.

Driver version 7.0 drops support for Java 7, which might be a problem in the future, but since version 6.2 will be supported until June 30, 2022, it is something to worry about later.