A lot of changes

Remove unused constructor of messages::Message
Fixed LimitedQueueSnapshot _-prefixes
Changed LimitedQueueSnapshot's usage of int to std::size_t
ColorScheme is no longer a singleton
Created a "BaseWidget" class which is pretty much a QWidget except it
has a reference of ColorScheme since most widgets will need a reference
to the style they should use.
BaseWidget can be implemented either with a BaseWidget parent (which
will copy the ColorScheme reference from the parent) or with a
normal QWidget parent and an explicit ColorScheme reference.
Save main window geometry on close
Fix font changing in the Settings Dialog
Update settings library version

src/ircmanager.hpp

@@ -10,6 +10,7 @@
 #include <QMutex>
 #include <QNetworkAccessManager>
 #include <QString>
+#include <pajlada/signals/signal.hpp>
 
 #include <memory>
 #include <mutex>
@@ -50,6 +51,8 @@ public:
     const twitch::TwitchUser &getUser() const;
     void setUser(const twitch::TwitchUser &account);
 
+    pajlada::Signals::Signal<Communi::IrcPrivateMessage *> onPrivateMessage;
+
 private:
     ChannelManager &channelManager;
     Resources &resources;