Improve usability of BNF/chemical pages for prescribers

[annapowellsmith]

Richard request. On e.g. https://openprescribing.net/bnf/0604 would like to see how Devon compares to the overall trend.

He suggested adding a CCG lookup box, and raw data line chart for CCG and national trends to BNF/chemical graphs (with a second y-axis to compensate for the difference between the CCG's numbers, and national numbers).

I suspect the answer may be better links through to /analyse and better UX to show national trends on the time chart on /analyse, rather than implementing new features just for this page.

[lmfrench]

There is already a link to the analyse page on the trends pages, but we could make this more obvious

[HelenCEBM]

Solved as per Lisa's comment (though could be made better in future)