OS Module created and Map module improved

I've add new module called OS to get possibility of showing platform betty runs on by asking it "show me OS name" or "OS name" or  just "OS". 
Somebody can say that such command is not very usefull for user, but I have three main reasons to add it. First - shell command for OS information is not very easy to remember("uname -a" for Linux).
Second - betty should know all possible requests and even little more I think)
Third - and this is main reason - some commands are depends on platform that user use.(as an example, "open" for MacOS and "xdg-open" for Linux).

I've also improved Map module to use right command for different platform.(as I said above "open" for MacOS, "xdg-open" for Linux, "start" for Windows(I sincerelly hope that betty will be used on Windows too:smiley:)).