reimplement wifi display hack with new external display SF framework

fix a few bugs with external displays

- HWComposer doesn't really handle multiple displays yet
  so there is a lot of ugliness there

- We also need to make sure that external displays are not
  blanked by default

- due to some EGL limitations surfaces being swapped need
  to be current

Change-Id: I82bff05b43bcebd8da863c7c76b4edbc3bc223a9