Fixes for updater plugin

Fixes problems described in the last comment of #233 
I added also support for the auto-restart mode in the BASH initialization script.
I wanted to add support for the autorestart mode  also to the Updater plugin but for me it's not working and I don't know why. This is what I get: 

```
141213 18:51:02	DEBUG	'AdminPlugin: OnSay handle 5:"!restart"'
141213 18:51:02	DEBUG	'AdminPlugin: handle command !restart'
141213 18:51:02	BOT    	'Shutting down...'
141213 18:51:02	BOT    	'Shutting down database connections...'
141213 18:51:02	VERBOSE	"RCON sending (127.0.0.1:33337) 'tell 0 ^0(^2b3^0)^7: ^8[pm]^7 ^7Shutting down for restart...'"
141213 18:51:02	INFO	'cron scheduler ended'
141213 18:51:03	BOT    	'Stop reading'
141213 18:51:07	BOT    	'Restarting...'
141213 18:51:07	BOT    	'Shutting down event handler'
```

and from stdout:

```
Running in auto-restart mode...
Starting www.bigbrotherbot.net (b3) v1.10.0dev.daily253-20141212 [posix] [PoisonIvy]

Using config file: b3/conf/b3_test.xml
checking for updates...
latest B3 dev version is 1.10dev.daily256

                 _\|/_
                 (o o)      1.10dev.daily256
         +----oOO---OOo-----------------------+
         |                                    |
         |                                    |
         | A newer version of B3 is available |
         |                                    |
         | http://files.cucurb.net/b3/daily/  |
         |                                    |
         +------------------------------------+


Using external plugin directory: /home/servers/test1/bigbrotherbot/b3/extplugins
Activating log   : /home/servers/test1/bigbrotherbot/b3.log
Connecting to DB : OK
Using Gamelog    : /home/servers/test1/urbanterror/q3ut4/test1.log
Testing RCON     : OK
Loading Events   : 38 events loaded
Loading Plugins  : ... (3)
Starting Plugins : ... (3)
Startup Complete : B3 is running! Let's get to work!

(If you run into problems, check /home/servers/test1/bigbrotherbot/b3.log in the B3 root directory for detailed log info)
Exited with status 0
Normal shutdown, stopping.
```

!restart should return exit code **221** and !die **222**. No matter what I type, the exit code is always 0. This would need to be fixed. I also think we should not use subprocess.call but using directly **POpen** and then invoke wait() on it. This because when a auto-restart is executed, a new shell is generated for the new process (we are using shell=True, also if it's adviced not to). This new shell process will have a new PID which would need to be copied in the b3 .pid file (in this way the bash initialization script will work nicely, together with in-game shutdown/restart commands).