Make grunt gfx work again

- remove WebGL.d.ts
- include lib.d.ts in references
- add missing interfaces in references

@mbebenita can you review this please? src/utilities needs lib.d, but lib.d conflicts with WebGL.d. Almost everything in WebGL.d is contained in lib.d, and i added the missing stuff to gfx/references. Any other reason you include WebGL.d?