Document how IDbConnection is managed

[benmccallum]

Further to this issue on core proj, documentation should explicitly state how the IDbConnection is managed.

Specifically, this comment, highlights three places that should be updated.

1. The readme under Setup Connection just new's up a SqlConnection without highlighting it'd need to be disposed.
2. The docs online under Query Factory should a similar story
3. The asp.net core example with DI is similar, but even worse, in that it looks like that's all you'd have to do, and the DI container, when it deconstructs the QueryFactory will just dispose the connection for you, but as we know, that's not the case.

However, if the core library changes to have IQueryFactory implement IDisposable, then the wording required would change.

Could we get an estimate on when documentation will get updated?