Implement search in frontend and use of real database storage in backend

[jhthorsen]

I would like to add support for Postgres/SQLite/MySQL in the backend and then add search in the frontend. The search inside plain files are too slow and unusable, so it wont't work.

This issue will also implement what is requested in the issues below, since using an indexed storage backend will allow us to save mor data:

• Trouble with participant list and /names #303 - Clicking on a notification element should take you to the correct place in the dialog
• Joins, parts, quits and nick changes not being displayed #355 - Joins, parts, quits and nick changes not being displayed
• Show mode changes #374 - Show mode changes

[jhthorsen]

We'll add /search command for the active channel which will search that conversation
The input field on /convos will search everything
The input field in a /:connection will search all conversations under that server

It will search from now and backward and feed data back over the websocket.

[jhthorsen]

Add special fields like on github: nick:xxx and user:xxx. Also a special search for finding links. See also #152.

[jhthorsen]

This is implemented in the backend: https://github.com/Nordaaker/convos/blob/one-point-oh/t/backend-file-messages.t

[Svetlana-T]

I would be glad to have this feature, too.

[Wikiwide]

Would be nice, as well.
Thank you.

[jhthorsen]

See #452 for search.

[jhthorsen]

Going to close this issue and rather create a new one for SQL based backend.