Bringing reference tables earlier

[znogbes]

Bringing look up tables before we set parameters would bring a more natural flow to our code and would facilitate QA.

I suggest these changes in branch set-up-categorical-filters:

In params.R:

• Source connections script after library upload
• Connections script will connect to data base(s) and bring reference tables
• References tables will be then available so analyst can procced to set date and categorical filters

[znogbes]

Addressed in https://github.com/nhs-england-patient-safety/patient-safety-data-request-template/pull/9