Sub-process piping

[vwbusguy]

Currently, stderr is shown more or less in real-time and stdout is presented only after a sub-process has ended. This means stuff like vim launches but the user must edit files blindly, making it virtually unusable. Similarly, dnf will seemingly hang indefinitely as it waits for a user to y/n confirm the changes. We need to present both stderr and stdout in realtime and, ideally, capture stdout separately in case it may be useful for piping later.