Also display the payload type of an exploit in exploits/show, if it defines one

[postmodern]

The exploits/show view should check if the @exploit includes Ronin::Exploits::Mixins::HasPayload and then display @exploit.payload_class by mapping @exploit.payload_class.payload_type to a displayable name (ex: Ronin::Payloads::ShellcodePayload.payload_type -> :shellcode -> Shellcode). See Ronin::Payloads::CLI::Printing for a mapping of payload classes to display names.