Convert PrefService to YAML

[ctrueden]

The (Default)PrefService is currently built on the Java Preferences API, which is platform-specific. Instead, we should use something human-readable and platform-independent. YAML is a good option. There is some code in ui-behaviour that could be a good starting point. See also this commit from TrackMate3 that works around a snakeyaml issue.

There is a question of whether we should bother to preserve backwards compatibility of preferences. It would be a one-time annoyance for existing users to have all their preferences reset.

CC @tpietzsch @acardona