Logger overhaul
Summary:
This moves ProxyLoggers functionality to the Logger base class and makes all important public functions static. Those functions then deliver the to be logged events to all objects of classes derived from Logger. This allows Amarok to have multiple Loggers.
I also added a DebugLogger which only gets build in debug mode and prints infos about all logged events to the console.
Reviewers: Amarok
Subscribers: Amarok
Tags: Amarok
Differential Revision: https://phabricator.kde.org/D11867