Finish preliminary offline support

* ProgressProvider now has an abort() call
* Abort button support added to the progress dialog
* YggdrasilTask and MojangAccount adapted to support abort

YggdrasilTask will time out after 10 seconds of no network activity, or when the user pushes the Play Offline button.
In offline mode, all instance update tasks are skipped! This will need further work.

1 files changed, 1 insertions, 0 deletions

diff --git a/logic/tasks/ProgressProvider.h b/logic/tasks/ProgressProvider.h
index f6f2906a..15e453a3 100644
--- a/logic/tasks/ProgressProvider.h
+++ b/logic/tasks/ProgressProvider.h
@@ -38,4 +38,5 @@ public:
 public
 slots:
 	virtual void start() = 0;
+	virtual void abort() = 0;
 };