New variables for blacklist

Here's a few variables which seem common enough to be worth of the blacklist.

These are provided by add-ons and are app-specific, so are useless in the JSON.

```
NEW_RELIC_ID
NEW_RELIC_LOG
NEW_RELIC_LICENSE_KEY
SEARCHBOX_URL
NEW_RELIC_APP_NAME
SENTRY_DSN
```

These are perhaps arguable, but it seems they still shouldn't be there by default.
```
LIBRARY_PATH
LANG
PYTHONPATH
LD_LIBRARY_PATH
PYTHONUNBUFFERED
PYTHONHASHSEED
PATH
PYTHONHOME
```

Thanks!