Added heartbeat system, improved payload UI, added generic reverse TCP shell.

[Renmusxd]

• Heartbeat system is made to deal with OSX laptop's socket behavior when closed/sleeping. Socket will appear to function normally from host side but will actually be suspended. I believe this was causing some timeout/out-of-sync issues when laptops were closed. Added a heartbeat system to check every 10 seconds that the client is still responding even if socket claims to be accepting bytes.
• Generic TCP Shell payload allows direct client - machine interaction and thus full terminal support. Payload detaches from parent process and masks itself with fork/exec
• Payloads now order themselves consistently.

[Renmusxd]

Had some free time so felt like adding some payloads and fixing some bugs.