Improve message search

Before starting a search was not fully obvious. One had to 1) click into the search text field and 2) hit enter.

• This change adds a dedicated search button.
• Highlights missing fields to start a search

Also adds

• An option to search for messages with arbitrary text

• An option to filter for outgoing and incoming messages (by nick or contact)

• New search logic to allow a new search whenever a search parameter has changed (instead of requiring to change the search entry field)

Screenshots

All	Contact (All messages)	Outgoing

Fixes #11964 (closed)