index session fix

after session expired it still showed logout instead of login button,
that is fixed now.
core.js fix

better error shown when steam inventory couldnt be loaded.
core.js replacement

i've added a replace part for the inventory viewer.

Some cards and backgrounds wants to put (Trading Card) or (Profile
Background) behind it's name, ive removed them now.
Merge pull request #4 from TheAnthonyNL/master

index session fix