Linux accel

Please check the comments in line 23. I didn't know which behavior was better, the choice is up to you.

Apparently there's no need to use evdev or stuff: according to IBM sysfs is reliable. You just need a glob to look for an accelerometer.
I'm not sure though about the range of the acceleration: on my PC it's from 1000 to -1000 (on android it's 10 to -10), but I don't know if it's related to the hardware used. I wanted to make it consisted so I simply divided it by 100, but if sysfs is not consistent we need to fix that and figure something out.

BTW I tested it and it works, at least with my accelerometer.
This is IBM's script I was talking about, where they use sysfs: http://www.ibm.com/developerworks/apps/download/index.jsp?contentid=150021&filename=knockAge-0.1.zip&method=http&locale=

(I forgot to checkout master before creating the new branch, I guess that if you merge this pr it will also merge the commits from the windows_email branch...)