Steam login added + show other  steam inventories

make sure that steam and www folder exists on your webserver (www can be
renamed to anything else) otherwise you have to change all paths.

also make sure that the "cache" folder in the steam folder is chmod 777,
so that we can save the json files from the people who logged in.
1. In order to get the login working make sure that all
"http://www.example.com" are changed into your server domain.
(session.php)

2. i have added more folders into the "data" folder which represents the
3 other steam inventories (gifts, coupons, cards). (still looking in how
i can improve this)

3. the core.js is modified so it makes it possible to load and show us
the other steam inventories.

4. at least make sure that the api key is defined in the
steam/apikey.php, lib/ie_L1.php and lib/steam_L1.php .

The login uses openid and is provided by steam, it creates a session
which expires after 15 minutes (can be changed but i left it default).
This session makes it possible that it loads only your inventory.

If there are questions please ask them, im willing to help you.
Merge pull request #3 from TheAnthonyNL/master

Steam login added + show other  steam inventories