Fixed display of failed operations.

Added encrypt/decrypt failed status messages.
Keep empty progress bar on failure screens.
miniLock.UI.animateProgressBarToShowError becomes miniLock.UI.fileOperationHasFailed
Let 'encrypt/decrypt:complete' event handlers be responsible for rendering the link to save, file size and identity of the sender.

Establishs miniLock.UI.fileOperationIsComplete as the worker callback for completed operations in symmetry with miniLock.UI.fileOperationHasFailed.

Removes the previous miniLock.UI.save callback.