This is to follow LRC/Qt naming convention. Getters don't begin
with the word "get".

Note that getBestId() has been kept so as not to break API, but
marked as deprecated so that we can quickly update the clients.

Change-Id: Ifcf1d66763b70b5ef4f1b67d39b40892263b5359
Reviewed-by: Nicolas Jäger <nicolas.jager@savoirfairelinux.com>