Split up core.other.js

[kharmabum]

Presently core.other.js includes a host of unrelated activities: gif search, emoji tokens, message actions, format commands.

• [ ] Create separate features for each core feature (gif.other.js, emoji.other.js, formats.other.js, etc)
• [ ] Make it the responsibility of core.other.js to ensure that core features are installed on the activity identity