cleanup about page handling and fix missing document.l10n

[bridiver]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

fixes #6012

Test Plan:
For each about page:

1. Load the page
2. Ensure that the page and favicon load correctly

[bridiver]

@bbondy @bsclifton

[bsclifton]

++ I like this 😎

[bbondy]

++

[bbondy]

Sorry I had to back this out because it was causing development builds to not see changes. webpack-dev-server doesn't know about gen.

[bridiver]

@bbondy gen is also the path for the webpack dev server. The change to the filtering code sends it to localhost or the file path depending on the env. I tested it and didn't see any problems, can you give me a specific example of something that didn't update?

[bridiver]

I just rebased it and tested updating preferences.js (for about pages) and main.js (for the main window) and both reloaded automatically