Add admin notification to description change

Value

Extend the DESCRIPTION command execution to include admin notifications so that other Admins know about the change of the description.

Behavior

GIVEN that an admin is changing the channel description

• WHEN DESCRIPTION command is successfully executed by an Admin
• THEN a notification goes to all Admins that says "Channel description set to $newdescription"

Additionally bug fixes:

• bump description to bottom of INFO output
• add test (in models/channel.spec.js) to confirm that empty string is set as default description field if none provided
• fix stray la canal in FR strings

Implementation Notes

Example translations for the notifications:

`Description de le canal définie sur "${$newdescription}."`,

`Descripción del canal establecida en "${$newdescription}."`,

`Channel description set to "${$newdescription}."`,