Add `--no-cache` option to avoid using Composer cache

[asgrim]

Since the repo data that PIE uses is actually Composer's I don't think we should have a clear cache command, but maybe add a command that suggests to use composer clear-cache to do that, and if interactive prompt to run it.

A useful addition though would be a --no-cache option to avoid using the cache; I believe this would be non-destructive to the Composer cache, so should be harmless.

Suggested originally in #309 (comment)