Remove empty space at the top of OpenGL pages

[TestingPlant]

This moves the bottom.php file to the index.php file, which seems to remove the empty space.

Fixes #92

[oddhack]

Sorry, overlooked this for a long time. Could you check if this is still happening? I just accepted an MR which fixes some PHP include paths, and the top subwindow now contains the navigation interface, as it should - I'm not sure if this is the white space you refer to though. Thanks.