Replace Welcome FAQ and data usage privacy URLs

[devinreams]

Merging into #430

To quadruple check all instances and get the revised anchor links in:

• "Learn more" on Welcome screen to #how-do-i-use-firefox-lockbox
• Send usage data "Learn more" on settings screen to privacy.html

Outside of this PR:

• No entries found on item details screen "Learn more" to #how-do-i-enable-sync-on-firefox happened at No entries state, prompt for authentication with FxA on other devices (mobile or desktop) to retrieve synced logins #44
• "Learn how to edit this entry" on item detail to #how-do-i-edit-existing-entries happened at Hook up edit FAQ link at bottom of entry detail #172
• No matching entries "Learn More" happening at "No Entries Found" state for search/filter #186

Depends on mozilla-lockwise/mozilla-lockwise.github.io#46

[sashei]

I would love to refactor the way we're doing FAQ links from the settings page so that we have only one SettingRouteAction associated.... :p might be out of scope for this story though.

[devinreams]

I would love to refactor the way we're doing FAQ links from the settings page so that we have only one SettingRouteAction associated

@sashei Yeah that's fair. Because I now added/proliferated .privacy which really just needs to be another constant URL pulled AFAICT.

I can back out the commit and look at what you have after #430 lands...

[devinreams]

I changed this to just be a ~3 line PR into @sashei's in-progress refactor at #172 #430.

So assuming it's OK then it'll all just go with that PR instead of having to be separate...