Add an FPS counter to core examples.
Add an FPS counter to core examples.

We can't use pyglet's text labels, so just print
to the console.

julienr/vispy,inclement/vispy,julienr/vispy,inclement/vispy,Eric89GXL/vispy,QuLogic/vispy,RebeccaWPerry/vispy,drufat/vispy,sh4wn/vispy,bollu/vispy,sbtlaarzc/vispy,ghisvail/vispy,hronoses/vispy,srinathv/vispy,dchilds7/Deysha-Star-Formation,kkuunnddaannkk/vispy,sh4wn/vispy,drufat/vispy,drufat/vispy,RebeccaWPerry/vispy,dchilds7/Deysha-Star-Formation,sbtlaarzc/vispy,kkuunnddaannkk/vispy,jay3sh/vispy,bollu/vispy,hronoses/vispy,sbtlaarzc/vispy,RebeccaWPerry/vispy,michaelaye/vispy,QuLogic/vispy,srinathv/vispy,sh4wn/vispy,ghisvail/vispy,julienr/vispy,hronoses/vispy,srinathv/vispy,jay3sh/vispy,bollu/vispy,Eric89GXL/vispy,QuLogic/vispy,jdreaver/vispy,michaelaye/vispy,ghisvail/vispy,jdreaver/vispy,inclement/vispy,kkuunnddaannkk/vispy,Eric89GXL/vispy,michaelaye/vispy,dchilds7/Deysha-Star-Formation,jay3sh/vispy,jdreaver/vispy