Encrypt and Decrypt Flags for "add" and "get" functions for CLI

### Checklist

- [X] My issue is specific & actionable.
- [X] I am not suggesting a protocol enhancement.
- [X] I have searched on the [issue tracker](https://github.com/ipfs/go-ipfs/issues?q=is%3Aissue) for my issue.

### Description

There is an obvious security hole here. As long as anyone has the hash of the PDF file, they can retrieve it from IPFS. So sensitive files are not well suited for IPFS in their native states. Unless we do something to these files, sharing sensitive files like health records or images is a poor fit for IPFS. So I want to add `ipfs add --encrypt --pub public.pgp` and `ipfs get --decrypt --private private.pgp` functionalities. For the passphrase or key locations, we can use config files on `~/.ipfs`

etc.
`cmds.BoolOption(encryptOptionName, "e", "Encrypt the given File")`

https://github.com/aydinnyunus/go-ipfs