Implement cache

[Flacy]

When installing the package, in order to avoid traffic consumption, it is necessary to add the caching feature, which will be enabled by default. Accordingly, additional commands are required to manage the cache, such as:

• Complete cache cleanup (fext cache purge)
• Remove a specific package from cache (fext cache remove package-name)
• Installing packages, avoiding caching (fext i requests --no-cache-dir)