msfcli - Added job execution

Able now to execute the module as a background job.

Original Idea: https://forum.intern0t.org/offensive-guides-information/3440-meterpreter-handler-persisent-connections.html



```
root@kali ~/metasploit-framework$ ./msfcli exploit/multi/handler PAYLOAD=windows/meterpreter/reverse_tcp LHOST=127.0.0.1 LPORT=4455 J
[*] Please wait while we load the module tree...
  +-------------------------------------------------------+
  |  METASPLOIT by Rapid7                                 |
  +---------------------------+---------------------------+
  |      __________________   |                           |
  |  ==c(______(o(______(_()  | |""""""""""""|======[***  |
  |             )=\           | |  EXPLOIT   \            |
  |            // \\          | |_____________\_______    |
  |           //   \\         | |==[msf >]============\   |
  |          //     \\        | |______________________\  |
  |         // RECON \\       | \(@)(@)(@)(@)(@)(@)(@)/   |
  |        //         \\      |  *********************    |
  +---------------------------+---------------------------+
  |      o O o                |        \'\/\/\/'/         |
  |              o O          |         )======(          |
  |                 o         |       .'  LOOT  '.        |
  | |^^^^^^^^^^^^^^|l___      |      /    _||__   \       |
  | |    PAYLOAD     |""\___, |     /    (_||_     \      |
  | |________________|__|)__| |    |     __||_)     |     |
  | |(@)(@)"""**|(@)(@)**|(@) |    "       ||       "     |
  |  = = = = = = = = = = = =  |     '--------------'      |
  +---------------------------+---------------------------+


       =[ metasploit v4.7.0-dev [core:4.7 api:1.0]
+ -- --=[ 1128 exploits - 638 auxiliary - 180 post
+ -- --=[ 309 payloads - 30 encoders - 8 nops

PAYLOAD => windows/meterpreter/reverse_tcp
LHOST => 127.0.0.1
LPORT => 4455
[*] Exploit running as background job.

[*] Started reverse handler on 127.0.0.1:4455 
[*] Starting the payload handler...
msf exploit(handler) > 
```