Ability to customize column sizes for subscription storage

[mookid8000]

Because column sizes are tricky when they are NVARCHARs and they are used in an index, it should be possible to configure the sizes.

It could look like this:

Configure.With(...)
	.Transport(t => (...))
	.Subscriptions(s => {
		s.StoreInSqlServer(..., "Subscriptions")
			.SetColumnSizes(topicColumnSize: 350, addressColumnSize: 50);
	})
	.Start();

which would then create the schema accordingly.

Moreover, a warning could be logged or an error could be thrown if the schema reflection in Initialize detects that the schema does not match the sizes specified in the Customize... thing.