Test Connection Strings should be configurable

[clupasq]

Currently, the SQL Connection Strings used for the tests are hardcoded in the src/Test/Config.cs file.

Not all contributors have a local database instance with the same name/credentials and I think it would be nice to provide some minimal flexibility in this case.

My idea would be to use some predefined ConnectionStrings settings that every developer would be able to configure in his/her local machine.config file. In case any of the necessary connection strings are not defined, we should fall back to the default (hardcoded) ones.

[sapiens]

I get what you're saying, but at this moment I think it doesn't bring any benefits. To be honest, I doubt that many developers would change their machine.config (which AFAIK requires a reboot) just to run some SqlFu tests. It's much easier to just change the connection string directly and then change it back.