Extension updates and edit command

[DavidSouther]

Adds several from #52:

Comand palette:

• Ailly: Edit Show an input box for the prompt. Use the current selection as line numbers. Send the prompt with edit and folder context. Replace content when finished (will overwrite any edits made while it's in flight).
• Appropriate usage of notifications for errors.

Explorer Context Menu:

• Ailly: Generate Generate file or folder in conversation context
• Ailly: Generate with Folder Generate file or folder in folder context

Settings:

• AILLY_ENGINE
• AILLY_MODEL
• LOG_LEVEL
• LOG_PRETTY