The tray icon appearance setting is null by default, since we do not
want to include OSUtils into Config. As a result, we must take special
care to preselect the correct combo box entry on the settings page.
Replaces all string configuration options with enum types
that can be checked by the compiler. This prevents spelling
errors, in-place configuration definitions, and inconsistent
default values. The default value config getter signature was
removed in favour of consistently and centrally default-initialised
configuration values.
Individual default values were adjusted for better security,
such as the default password length, which was increased from
16 characters to 32.
The already existing config option deprecation map was extended
by a general migration procedure using configuration versioning.
Settings were split into Roaming and Local settings, which
go to their respective AppData locations on Windows.
Fixes#2574Fixes#2193
