The recent change to parse the channel from a Repost using a `claim` ended up breaking the case for abandoned claims, which `claim` will be `null`.
Fix by looking at `claim` first (faster), and falling back to the `parseURI` method if it remains inconclusive.
## General
- `setting.List`: returns full creator settings. Requires signature (i.e. you own the channel)
- `setting.Get`: returns a public subset of the creator settings. No signature required, and it is mainly used by the GUI to determine the constraints of a channel (e.g. comments enabled? min tip requirements? etc.). Does not include private settings like "blocked words list".
`doFetchCreatorSettings` will handle both of these. Clients that uses the stashed results (`settingsByChannelId`) just needs to be aware the result might not contain everything, depending on whether you own the channel or not.
## Misc Related Changes
- Finally fix the reducer for COMMENT_FETCH_SETTINGS_COMPLETED to not purge the data on each call.
- Change `doFetchCreatorSettings` to operate on a single channel instead of multiple. We ended up not using the multple mode anyway, so it was wasteful code trying to batch the promises.
- `commentsDisabledChannelIds` is no longer needed. Previously, this was created just to differentiate between Creator (full) and Channel (subset) settings. It's cleaner to just use one object, so eliminated this.
- Remove unused 'commentingEnabled'.
## Aside
- There are now 2 ways to know if a channel has disabled comments: (1) from `comment.list` and `setting.Get|List`. Both of them updates `settingsByChannelId`, so it'll still be a single place for the GUI to check against.
