Port CEF 1 examples to CEF 3

[cztomczak]

There are some useful examples in CEF 1 that should be ported to CEF 3. CEF 1 code has been removed from master, but is still available in the cefpython31 branch.

1. cefadvanced.py example that uses pywin32 has some unique features:
   • javascript rebindings
   • key handler for F5 F12 F11 Ctrl+ Ctrl-
   • saving browser window content as an image
2. More examples that should be ported:
   • cefwxpanel
     • https://github.com/cztomczak/cefpython/blob/cefpython31/cefpython/cef1/windows/binaries/cefwxpanel.py
     • https://github.com/cztomczak/cefpython/blob/cefpython31/cefpython/cef1/windows/binaries/cefwxpanel_sample1.py
     • https://github.com/cztomczak/cefpython/blob/cefpython31/cefpython/cef1/windows/binaries/cefwxpanel_sample2.py