Use X-Terminal as the REPL

[aminya]

X-terminal:

• uses the terminal shipped with the operating system which is way faster.
• It is continually updated, so we receive the optimization and bug fixes for free
• Makes Juno more modular by removing this part of the code. Ink will become way lighter. We should move potential missing features there.
• Let other languages make use of this code!

Not every language package should make a Terminal for itself.

PlatformIO, the IDE for C/C++ already does this: https://github.com/platformio/platformio-atom-ide