Simplify role-changing machinery with json and js

[eteq]

Right now it's a bit awkwardly complicated to update the roles - you have to update a special-format roles.txt file, and then run a script locally and remember to commit both with git. That works for now, but A better system might be to:

• change roles.txt to a roles.json file
• use code like what we have in the affiliated package page to populate a table from the JSON using a javascript function (which would run locally and is very fast - this has been in practice very stable/easy on the affilaited/index.html).
• include the roles descriptions in theroles.json as well - then do a bit more js tricks to get the roles list to appear on the web site.

Once these are all done, it'll be easy to update the roles in a single commit rather than the awkward 2- or 3- stage process currently required (which also requires knowing to run the script).

Also #167 could be much more easily addressed with this all in place - there could be an additional json field for past holders of the role, and the js could include that at the bottom of the page or something.

[apooravc]

@eteq Working on it.