--profile should work with --all-profiles

[jgard]

Currently if you use --all-profiles, you get named profiles <AWS Account Alias>-<IdP>-<Role>. In our situation (and I'm guessing many others), that <AWS Account Alias>-<IdP> is the same for everyone at our company and is unnecessarily long and not particularly useful. In this situation, I would like --profile to do one of:

• Simple, just the prefix before the Role Name. I would just use base personally, ending up with base-<Role>.
• A more elaborate variable interpolation string with identifiers for the known values. Like %A-%I-%R might result in the current behavior, but I'd just use base-%R