Emoji Picker should be refactored into `App.EmojiPad`

[Marak]

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The current emoji picker interface is pretty OK, but it acts like a popup window and should instead act like a regular desktop window.

To do this, we'll want to create a new app called App.EmojiPad which shows the emoji picker.

If App.EmojiPad is opened from a chat window, it will have a context such as "Lily". This context can be used to direct the output of emojis from App.EmojiPad to the appropriate / active chat window. The other apps that work with chat controls already have this logic. It should be easy to add.

If App.EmojiPad is opened as a stand-alone app ( without context and not from chat window ), then the emoji picker should show with a small textarea below it that shows the emojis outputted.

[Marak]

https://github.com/mervick/emojionearea is also a consideration for App.EmojiPad