Implementes --uninstall option

Examples:

```
$ cpanm --uninstall LWP::UserAgent
$ cpanm --uninstall LWP::Protocol::https Net::SSLeay
$ cpanm --uninstall --quiet Moose
$ cpanm --uninstall --force Plack # no prompt
$ cpanm --uninstall -L local Amon2
````

But currently not removing `.meta` directories...