refactor(client): Simplify url.js->searchParams
refactor(client): Simplify url.js->searchParams

* Use _.pick to filter the fields.

shane-tomlinson/fxa-content-server,swatilk/fxa-content-server,shane-tomlinson/fxa-content-server,vladikoff/fxa-content-server,vladikoff/fxa-content-server,mozilla/fxa-content-server,swatilk/fxa-content-server,vladikoff/fxa-content-server,mozilla/fxa-content-server,shane-tomlinson/fxa-content-server,swatilk/fxa-content-server,mozilla/fxa-content-server