CDAP Component, Package and Property Names don't align

Description

There are a number of places in the documentation where we talk about "gateway" and "router", "dashboard" and "console", as if the former terms were synonyms for the latter. They aren't exactly, and their use in package names and properties is inconsistent and confusing. However, changing these names – because they are embedded in the code – is non-trivial.

JJ talked to Terence and Andreas about this. Andreas tried a month ago to get rid of one of "router" and "gateway" and found he couldn't. Those properties are still needed and used.

So consensus was the best we could do would be to rename "cdap-gateway" to "cdap-router" and gloss over the exposure of "gateway" in the XML file. Eventually we might be able to rename those properties, but that would be a bigger undertaking.

So, we should try to:

replace "cdap-gateway" as a package name with "cdap-router", and change the distribution and the documentation to suit;
replace "cdap-web-app" as a package name with "cdap-console", and change the distribution and documentation;
see if the properties can be changed in the cdap-site.xml, and replace "gateway" with an augmented "router" name, and "dashboard" with "console".

Alternatives would be "web app", "web-app", and "console" become "dashboard"...