Popup for notifying the user of exercises that can be updated

[nucularmoo]

If we continue on the idea of adding icons into the TMC results pane bar, could add icon for updating exercises that would normally be grayed out, but color up when there are updates to be downloaded.
As the plugin will occasionally poll for updates and when the updates are available, a small popup would be nice to inform the user that there are exercises to download.
However the popup should not become active as in steal your cursor and should more be a notification type that will allow the user to update/dowload exercises (to not interfere with the user workflow)

[kimmoal]

Currently the popup contains a list of exercises that are not downloaded. This gets annoying because if you choose not to download them all at once, the window keeps popping up when you have unfinished downloads. This should be changed to a bit less intrusive Qt Creator "native badge" that is currently popping up whenever we do the update.