Change the default option for the unsafe paste dialog back

Issue #311 (closed) proposed a change to cancel the unsafe paste dialogue by default. Commit 273d0cfd implemented this change.

There is no explanation, but it was a big enough problem for me that I tracked it down in the source.

I disagree with the change:

1. This has destroyed my muscle memory. I was used to seeing the dialog, quickly looking at the contents of the paste, and hitting enter.
2. It is not safer to cancel by default. If I mindlessly mash enter after pasting into a terminal, I clearly don't care about the contents of the paste.
3. It is both redundant and unintuitive. The escape key has always been bound to canceling the paste:
   • With the old behavior you could press ESC to cancel or ENTER to paste.
   • With the default option as cancel, you can press ESC or ENTER to cancel the paste, but to accept it you now have to press right arrow then ENTER.

I propose 2 possibilities for fixing this:

1. Change the default behavior back by reverting 273d0cfd.
2. Add an option in the settings, as changing the default option back to accept might actually be dangerous now.