Convert cosmetic commands into proper interfaces

[Rosy-iso]

Description

Adds an interface that replicates the behavior of the following commands:

• /myroomavatar
• /myroomnick
• /color
• /scolor
• /pronoun
• /spronoun
• /font
• /sfont

The original commands will still remain and be usable however.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings