Reimplement the search
This patch reimplement the search doing a simple for-loop with a regex to search in the list of messages and updating the interface just when the message is found.
A following step could be to do this async, in a different thread, so it won't freeze the interface for large files, but for now this solution should be good enough, and should improve the search a lot.
Fix #194 (closed) See #144 (closed)