improve nomenclature consistency

[AndreaSanchezTapia]

• Vessel IDs, vessel IDs, vesselID (in the table), and VesselID (in the documentation) are spelled in many ways in different places.
• the parameters are called as id in get_vessel_info() and vessels in other functions
• they're named id or vesselId in the API results (selRepoortedInfo$id, combinedSourcesInfo$VesselID but there are other fields named id in the returning datasets that are not vessel IDs like registryInfo$id

Possible discussion with the API team as well to avoid solving downstream.

[AndreaSanchezTapia]

The tinyest change to avoid a long explanation is renaming selfReportedInfo$id to selfReportedInfo$vesselId in the results. No change to parameters or API calls, only readme and vignette results processing.

[AndreaSanchezTapia]

• readd the explanation that ssvid is MMSI in the case of AIS

[jflowernet]

Hi. Hope you don't mind me jumping in, but I had a thought about argument naming! I notice in the latest version of gfwr, get_raster() has had some changes, one of which is that the user specified region should be an sf object (great enhancement, thanks!). Given this change, wouldn't it make sense to use region_source = "user_polygon", or something similar, rather than "user_json"?

[AndreaSanchezTapia]

Thanks for flagging this, @jflowernet ! I made a correction to USER_SHAPEFILE.