Fix #3914 - Inconsistent unicode names
Msfpayload doesn't work if ENCODER option is set
Delete Encoder possibility in msfpayload
Remove nonfunctional jtr_unshadow

This module hasn't been doing anything but print_error a go away message
since June, so may as well get rid of it.
space after commas
Land #3919, @wchen-r7's Fixes #3914, Inconsistent unicode names
Land #3970, rm jtr_unshadow
Land #3920, @agix's removal of dead encode code from msfpayload.

Was originally supposed to add support for encoders, but
this was never a supported feature of msfpayload.