Git: Support graph log for all log types (file, project, repo)

* Added a Graph toggle button for log editor
* Hide diff parameters when Diff is off
* Remove GitClient::graphLog

Change-Id: Ib87560bc4d6d7dbe866f0e58db8743a95df0622b
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/git/gitplugin.h

@@ -113,6 +113,7 @@ private slots:
     void logFile();
     void blameFile();
     void logProject();
+    void logRepository();
     void undoFileChanges(bool revertStaging = true);
     void undoUnstagedFileChanges();
     void resetRepository();