Checking using `settings.Allowed` is odd. Not all commands are related
to setting configuration settings. Admin commands are coming in the
future, for which this is certainly not the case.
We now do access checks early on (during command processing), so command
handlers can be clean of access checks. If we're inside of a command
handler, the user is privileged to run it.
Retrieving the settings object for each and every option was wasteful
I don't like how we're doing custom formatting for optionMailbox in many
different places. This should be redone.
Before:
> * **`!pm help`** - Show this help message
> * **`!pm stop`** - Disable bridge for the room and clear all configuration
> * **`!pm mailbox`** - Get or set mailbox of the room
> * **`!pm owner`** - Get or set owner of the room
> * **`!pm nosender`** - Get or set `nosender` of the room (`true` - hide email sender; `false` - show email sender)
> * **`!pm nosubject`** - Get or set `nosubject` of the room (`true` - hide email subject; `false` - show email subject)
> * **`!pm nohtml`** - Get or set `nohtml` of the room (`true` - ignore HTML in email; `false` - parse HTML in emails)
> * **`!pm nothreads`** - Get or set `nothreads` of the room (`true` - ignore email threads; `false` - convert email threads into matrix threads)
> * **`!pm nofiles`** - Get or set `nofiles` of the room (`true` - ignore email attachments; `false` - upload email attachments
After:
> * **`!pm help`** - Show this help message
> * **`!pm stop`** - Disable bridge for the room and clear all configuration
> * **`!pm mailbox`** (currently `something@example.com`) - Get or set mailbox of the room
> * **`!pm owner`** (currently `@someone:example.com`) - Get or set owner of the room
> * **`!pm nosender`** (currently `false`) - Get or set `nosender` of the room (`true` - hide email sender; `false` - show email sender)
> * **`!pm nosubject`** (currently `true`) - Get or set `nosubject` of the room (`true` - hide email subject; `false` - show email subject)
> * **`!pm nohtml`** (currently `false`) - Get or set `nohtml` of the room (`true` - ignore HTML in email; `false` - parse HTML in emails)
> * **`!pm nothreads`** (currently `false`) - Get or set `nothreads` of the room (`true` - ignore email threads; `false` - convert email threads into matrix threads)
> * **`!pm nofiles`** (currently `false`) - Get or set `nofiles` of the room (`true` - ignore email attachments; `false` - upload email attachments)
