Prefix per server

[itsTheFae]

• [x] I have tested my changes against the dev branch (the latest developmental version), and this pull request is targeting that branch as a base
• [x] I have tested my changes on Python 3.10.12
• [x] I have ensured my code is formatted using Black

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Description

This PR adds support for setting a command prefix per guild/server. It adds one new option EnableOptionsPerGuild and a new command setprefix to manage the feature.
This feature allows just about anything without spaces to be set as a command prefix, including Emoji. Only one verb cannot be set, as setprefix clear is used to clear any currently set prefix. The default prefix in options.ini is used when no server-specific prefix is set. If per-guild options are not enabled the setprefix command will raise an error.

Additionally, this feature will remember a limited number of prefix changes so the clean command can take care of messages prior to a prefix change. This history of prefixes does not persist through restarts.

Related issues (if applicable)

2288

[itsTheFae]

This should be fully ready to go now. :+1: