Recoding for templates

[aspina7]

This is for recoding non-standard data to be able to use the analysis templates - addresses #322

Currently evaluate is sett to FALSE for all code chunks in the recode templates as do not want to run tests on these, given that there is no associated dummy data and thereby all tests will just fail.

these templates will:

• refer to vignette that walks through the process
• code chunk for renaming necessary variables
• code chunk to see variable and values from the standard dictionary
  • (shorten existing study_data_dict_long to just varname, vartype, value)
  • potentially combine with above function to see which variables actually necessary for the template
• code chunk to see all their unique values from messy data
• generic recode for factor variables example.
• generic example for recoding age and other ??

age recoding probably needs checking .... just did quickly

[PBBlomquist]

I've reviewed and thought some changes were needed for clarity and to align with outbreak recode Rmds.

I've just done the AJS one and put it in a different branch/commit just in case. Changes made are:

• some chunk rearrangement and simplification to be more straight forward (renamed some chunks as needed)
• Removal of summarytools as doesn't work
• Clearer/typo-free explanations
• Age calculations corrected (note still need to check 2 months = 62 days or 56? Show years at 24 months onwards?).