adds predenominated to ensure raw measures are returned

[andy-esch]

This PR adds non-denominated measures (aka raw ones) to the metadata response.

ToDo

• metadata returns non-denominated ("predenominated") values as well as derived quantities
• add pgquote function to turn strings to single-quoted strings and Nones to nulls
• ensure that the metadata table is a set (no duplicates) --> it seems that duplicates are not returned from metadata, but this could easily be fixed by adding a distinct to the obs_getmeta call.

closes #324

[coveralls]

Coverage remained the same at 97.309% when pulling 0997ead on iss324-data-discovery-raw-data into d2e9017 on master.

[coveralls]

Coverage increased (+0.006%) to 97.315% when pulling fd9c3c3 on iss324-data-discovery-raw-data into d2e9017 on master.

[coveralls]

Coverage increased (+0.006%) to 97.315% when pulling fd9c3c3 on iss324-data-discovery-raw-data into d2e9017 on master.

[coveralls]

Coverage increased (+0.006%) to 97.315% when pulling fd9c3c3 on iss324-data-discovery-raw-data into d2e9017 on master.

[coveralls]

Coverage increased (+0.006%) to 97.315% when pulling fd9c3c3 on iss324-data-discovery-raw-data into d2e9017 on master.