Update DBConnection to version 2.0

[whossname]

I have started work on updating Mssqlex to use DBConnection version 2.0 (https://github.com/whossname/mssqlex/tree/db_connection_2.0)

I believe this is the first step towards Ecto 3 support in mssql_ecto. (findmypast-oss/mssql_ecto#43).

This is likely to take me a fair amount of time as I will be doing it in my spare time, and still don't really understand how DBConnection and Mssqlex work. I'm mostly just working on getting the tests to work at the moment.

[whossname]

I've at least got all of the tests passing (https://travis-ci.com/whossname/mssqlex).

[jbachhardie]

Thank you very much for tackling this. Submit a PR when you're ready and I'll prioritise reviewing and merging it.

[whossname]

I've started working on the mssql_ecto stuff now (https://github.com/whossname/mssql_ecto/tree/ecto_3.0).

I'm seeing errors in the tests in that repo that look like they are caused by my branch in this repo.

Didn't get far this weekend, I'll see how I do next weekend.

[whossname]

A quick update on this. I haven't really had much time to work on it over the last couple of weeks, and don't expect to have much time for it in the next few weeks. I'm reasonably confident that what I'm doing with mssqlex is along the right track, but mssql_ecto still needs a lot of work. I hope to get to it at some stage in the next month or two.

[pcharbon70]

I am really looking forward to this so a big thank you in advance from me too. Having some random disconnect issues from Db_connection and hoping this might help :)

[whossname]

As mentioned in findmypast-oss/mssql_ecto#43 this isn't the main issue in updating to Ecto 3. I think this issue is pretty much already addressed on my branch of mssqlex. I won't make the pull request until I've got a version of mssql_ecto working for Ecto-3

[whossname]

This pull request #24