Fixes State.saveUniquely throwing validation exceptions when there are lots of threads using it at once.
Fixes NPE when ImageResizeStorageItemListener can't access the image.
Fixes connection close from SqlDatabase when using cacheData in highly concurrent situations.
Adds Closeable implementation to SqlDatabase.SqlIterator.
Merge branch 'release/2.0'
Changes AbstractStorageItem to ignore errors caused by listeners on save.
Merge branch 'master' into feature/metric