Allow some way to force install

[FoamyGuy]

Currently circup install [whatever] will fail if [whatever] is already installed, even if it's an old version or an old mpy version that is no longer functional.

It would be nice if we could circup install --force [whatever] and it would do the install even though there was an old version installed.

Or perhaps alternatively circup update could be made to support a single library as an argument to update just one instead of all of them.