Add scripts to remove old AMIs we have uploaded

[ralphbean]

We need a script to run as cron that will remove old AMIs we have uploaded.

• We should keep the last month of AMIs, generally.
• We should keep the GA final release AMIs forever.
• The Alpha, Beta, and TC RC releases might should be kept for a month or two.
• All other AMIs should be deleted after they've been up for a month.

[ralphbean]

@mattdm says we maybe don't have to worry about this. Ask matt. :poultry_leg:

[ralphbean]

If we do decide to close this, let's do so.. but make sure to tell dgilmore and the #fedora-releng crew about the decision.