`corectl python-console`: can't choose interpreter

Current behavior of `corectl python-console` uses the first available interpreter in this order of preference: `bpython`, `IPython`, then built-in interpreter.

An user could have both `bpython` and `IPython` installed and still prefer to use IPython.
But from now the only way to use IPython in `corectl python-console` is to uninstall bpython from system.