Sending Ctrl+C (SIGINT) shouldn't close child process

[epiccurious]

During the IBD process, the user can close the terminal window and just run Bitcoin Core; however, if the user sends Ctrl+C, bash will both stop the script and close the child process (Bitcoin Core).

Set up a trap SIGINT function to that will exit the script gracefully.

[epiccurious]

Removing from MVP.

[epiccurious]

This issue is blocked, pending the resolution of #10.

Setting Core to run as a service would solve the Ctrl+C issue.