Deprecate 3 unused Django settings

[chosak]

This commit deprecates 3 unused Django settings:

OFFLINE_OUTPUT_DIR = ''
GOOGLE_ANALYTICS_ID = ''
GOOGLE_ANALYTICS_SITE = ''

These were all added back in April 2016 (in commit b859cc8) but as far as I can tell are not used anywhere. Therefore we can remove them.

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code follows the standards laid out in the CFPB development guidelines

[anselmbradford]

Maybe intended for #495 ? Would it make any sense to use the Google variables versus removing them?

[chosak]

@anselmbradford definitely a good idea! Since we have that issue open as a place to track it, though, I'd prefer to delete for now and re-add when we pick that back up.

If it's the case (as it seems to be?) that we're using the same Google ID in the base.html template and so every page in every cf.gov request -- production, beta, internal, even local development? -- record that traffic to the same GA account.. and that's been happening since you opened #495 in 2015? that seems like a bigger problem. Pinging @sonnakim for awareness.