what file tells the context menu what buttons should be in it, in certain situations. Like when I press white while in my files I get one button setup but if I press it in my videos i'll get a different button setup.

Nothing in the skin its hardcoded into XBMC and unless yo can compile your own and know a lot of C++ you wont be able to change it

That sucks I would have really liked to add a "queue all" button in there when in my music or my videos.

why not just navigate to the parent directory and press 'Y' or 'Zero'