Add global attribute for ROR and update guidelines for institution #52

Add a field, something like "institution_ror," which contains the ROR IDs for each of those institutions in the "institution" field, separated by semicolon, and blank if no ROR ID for the particular institution. The institution field should then be populated with the institution name as it appears in the ROR database, using semicolons to separate institution names, if there are more than one. cc @apkrelling @MathewBiddle