change `ejam2report()` call in /get report endpoint to allow API handle specific site

[ericnost]

Change https://github.com/edgi-govdata-archiving/EJAM-API/blob/fc4128212c3b9119f56f0e24496347e5da42a983/rest_controller.r#L167 to sitenumber = sn and https://github.com/edgi-govdata-archiving/EJAM-API/blob/fc4128212c3b9119f56f0e24496347e5da42a983/rest_controller.r#L135 to default sitenumber = 1 but allow user in API call to pick any number for sitenumber. Then, in EJSCREEN (?), make sure site id gets passed and lines up.

[ejanalysis]

By the way, this is only relevant to when the API is called from within EJAM, not for reports generated from the EJSCREEN "Report" tab, since only EJAM is multisite and handles a set of sites with sitenumber 1 through N. So EJSCREEN Report functionality does not really have to change anything. Just the API would change in case it is getting used by EJAM and a sitenumber is being passed from EJAM.

[ericnost]

That makes sense. Good to know! It makes things a lot easier.