fix server frametime graph, was using the constant delta time

that is present in the fixed timestep game loop. also better handle
*huge* lag spikes, server-side. that is, contnue pumping the network, and
also flushing it so we don't get backed up.
fix rendering of graphs (background framebuffer garbage), fix servertime graph

some more. since dt is actually constant, we just report our frametime
difference that it takes for us to get there. that *should* be more useful
than a constant 16.6666 value. by how much, i do not know. but eg sleeping
for 10 msec in the server thread on mouse click results in a nice graph spike.
obviously that's a bit extreme, but should aid in detecting hitches.
lots of server timer/time fixes

also no need to call update on fboinsgrenderer node, apparently.
remove the extranous 2 signal/slot connections in fbosgrenderer

it's a hot loop, i'm sure it has some hit, even if it's a direct connection
either way, it's cleaner this way and less confusing.