Core update notification is displayed for all user levels

[johnbillion]

Every user of the admin panel sees the core update notification if there is an update available. It should only be displayed to users who have a sufficient capability. Not quite sure what though, maybe switch_themes?

Only display core update notification to users with the switch_themes capability

Patch to only display core update notification to users with the switch_themes capability.

Apply same logic for the admin footer

Patch for footer too. Just display the version number.

manage_options is another option.

What if the administrator infrequently logs in? Authors who don't have FTP/SSH access could tell the administrator of the message, hastening the upgrade. We could to the manage_options test and to unpriv'd users say "Please notify the site administrator"

Replaces 2 previous patches, Check for manage_options capability, advise unpriv'd users to notify site admin, fix indentation

Replying to markjaquith:
Excellent point Mark. Patch refreshed.

+1 This looks good.

(In [5994]) Check manage_options for upgrade notification. Tailor message accordingly. Props johnbillion. fixes #4869