Feature request - better package management interfaze

Allow to arbitrary update for included libs
this is a simple idea, allow the developer to request an environment update for a specific library, something like:
`p4a upgrade # to cast an update for every lib`
`p4a upgrade lib1# to cast an update for lib1`

This would save time for people who's working with a specialized or private dependencies that need to be updated to fix an issue on the final app that it's not caused by the app's implementation, instead of having to download everything again.

Start at the p4a command-line entry point and trace the existing package-management flow; no file or test is named in the issue. Done means supporting an update request for every included library and a request targeting one named library, without downloading everything again.

Written by the indexing model from the issue text.