prevent disabled packages from triggering status view updates

[zoo1]

Description of the Change

Check when a package update is available if it is disabled and prevent a status view alert.
Fixes #956

Benefits

Remove unnecessary update noise to users.

[winstliu]

Looks like I labeled that as a bug a bit too hastily. Looking back, I think this is expected behavior: there is still an update available for the disabled package, and we should probably be displaying that in the status view.

@KSXGitHub is there any reason why you think disabled packages shouldn't be displayed in the status bar?

[KSXGitHub]

@50Wliu There is no reason I would want to frequently update a disabled package because I do not use it frequently. If I really want to update a disabled package, I can just go to settings view or just use apm.

Looking back, I think this is expected behavior

I think you should label #956 as a feature rather than a bug

[winstliu]

Ok, I now agree with this change. However, there needs to be additional logic in onPackageUpdating and onPackageUpdateFailed to add the disabled package to this.updates. Either that, or adding the disabled check to all the on* methods. Also, specs will be needed.