evolution: improve out-of-gnome use

Add `evolution_data_server` to `propagatedUserEnvPkgs`. Evolution needs
`${gnome3.evolution_data_server}/libexec/evolution-source-registry` to
be running to be able to find or create any account settings at all, and
it apparently doesn't know to start it if it's not in the user env.

Use `makeGAppsWrapper` instead of a custom `wrapProgram` invocation.

Add `glib_networking`, `libgnome_keyring` and `dconf` to `buildInputs`.
`libgnome_keyring` appears to be necessary for evolution to remember a
password even for a single session, even if it doesn't get added to the
keyring permanently. `dconf` is necessary to persist preferences.
`glib_networking` is necessary to connect to mail servers.