Change field names in search UI pages

[ljwh2]

On study pages:

• [ ] In study information box: Replace “Discovery ancestry (country of recruitment)” with “Discovery ancestry label (country of recruitment)”

“Replication ancestry (country of recruitment)” with “Replication ancestry label (country of recruitment)”

• [ ] To this text above, add "?" with hover text "What is an ancestry label?" and link to https://www.ebi.ac.uk/gwas/docs/ancestry (noting url will change, see goci#1389)

• [ ] If possible, add the same hover to Studies table to the header of the sample column as shown (red is just for illustration):