Error Handling: setup error handling across the app

Needs #52 #53 to start work on this.

Any call to getGoogleSheet should be handled globally. This way we can keep track of errors more easily and output them to the admin's error page.

This is how things _should_ work after this PR:

1. When the app loads, the **entire** google sheet is pulled. This is available globally.
2. After we get the google sheet, we need to test every category / service to make sure it is valid (not missing a category, has correct references, etc.) Utils for this will be done in #52
3. If a category / service is invalid, it will be removed from the results and the error will be logged on the `/errors` page, where admins can see warnings and errors about the sheet. See #53
4. A link should appear on the home page with text along the lines of: "There was an error processing your data. Site admins please see the `/errors` page" (There should already be a component for this)