FEATURE: Support for Oracle

[mdenwood]

Add support for Oracle

It would be great to extend SCDB for use with Oracle; specifically using the RJDBC driver.

Our specific use case is our internal database holding CHR and VetStat data (http://github.com/ku-awdc/vetstat).

[RasmusSkytte]

Hi Matt

I wanted to let you know that I have been spending some time on getting SCDB to work with Oracle -- also more time than I would have liked given the progress I have gotten on the issue.

A status update:

We have a workflow running with a Oracle DB to test against (this was much harder to achieve than I could reasonably have expected).

I have started to adapt the SCDB to work with RJDBC.

Here there have been a lot of troubles:

1. we use dbplyr to translate from R to SQL which does not have good RJDBC support
   (although they seem to be working on it)
2. The RJDBC driver for R (https://github.com/s-u/RJDBC/) is seemingly abandon-ware and we really want to use the functionality on their dev branch. (They have released 0.3.0 elsewhere but only 0.2.0 on CRAN, which cannot extract the numeric type from the database)

Overall, I have an idea for fixing most of it, but since we can only develop via actions on github.com, it is not fun to do and I am taking a break from further working in this (hoping that someone else will implement the translations properly)