Consolidate usage of Gateway and Router in documentation
Description
We're in the process of deprecating Gateway (i.e. for flume ingestion).
However, we still sometimes interchangeably refer to Router as Gateway, and vice versa in the documentation (including ingest and auth clients). We should consolidate the usage to a standard - to probably just Gateway.
The only remaining use of the word "Gateway" in the documentation is in the cdap-site.xml file documentation, where there are properties with the word "gateway", and the descriptions use that word. We will leave the properties as-is for now, but change the descriptions.
We're in the process of deprecating Gateway (i.e. for flume ingestion).
However, we still sometimes interchangeably refer to Router as Gateway, and vice versa in the documentation (including ingest and auth clients). We should consolidate the usage to a standard - to probably just Gateway.