campaign and entrypoint are only imported for the fx-desktop relier & needed more generically

[shane-tomlinson]

The code to import the campaign and entrypoint query parameters lives in the fx-desktop relier.

From the marketing team in bugzilla #1162192:

This is important as we use the spring 2015 campaign to drive users to create Firefox accounts. We don't currently have a landing page to drive users to, so as our various channels (social, email and snippet) encourage Firefox Accounts creation, we need a way to measure conversions for testing and optimization purposes.

and

We want to track the number of accounts created on that page by source. So if we were using GA, we'd have UTM tags in our various URLs to the page that would allow us in GA to create a breakdown of which channel drove x number of conversions. Email xx percent of total YY and social / Facebook zz percent of total yy and so on.

and

Hey team! Similar to how we can directly track back campaigns and content to Firefox downloads, our hope is that we can do the same thing with Accounts. It would be valuable to identify what kind of content works, and what kind of content doesn't in driving accounts sign ups.

A first step is to import these values from models/relier.js instead.

How we surface this information to the marketing team is a different question.

[ncalexan]

Android and iOS would like to use entrypoint, or something similar, to track whether our first run experience is driving Account flow volume. We're very interested in whether new users complete the flow.