Bump `cef.sdk` package to 3.2062.1876-pre1 with VS2013 specific libs too

BTW I guess we have to exercise "the split" on x86/x64 a bit on this branch with how it affects NuGet users (and prepare some communication?). We can use `CefSharp.MinimalExample` + start from scratch scenarios like the one painfully documented  in #520 for that.

Maybe we can even move `CefSharp.*` packages a bit more towards a more normal NuGet structure with `lib` folders and such? We just need to find a way to make sure we can still install both `x86` and `x64` in parallel - or should we go for a `AnyCPU` package? 

Hmm - forgive me for thinking out loud above - I hope *some* of it brings us forward though ;)
Should this include the `-pre` tag? I can't remember