Added CefSharp.Offscreen, CefSharp.Offscreen.Example projects.

[jankurianski]

Please run CefSharp.Offscreen.Example project to test this out (it is a Console application which takes a screenshot of the Google homepage).

I have ensured everything works in Debug/Release and x86/x64 mode, however I am unsure about the nuget packages as I don't know how to build them (and was hoping someone else could tell me if it works 😉).

Addresses issues #577, #518 (sort of; about printing, but screenshots may be acceptable), #462.

[jankurianski]

Oh dear, adding the new projects has made AppVeyor angry. Anything I can do to fix that?

[jornh]

It says Failed — AppVeyor was unable to build non-mergeable pull request so apparently some sort of merge conflict - so make sure you are based on latest master

But it's not the end of the world. It's what we have them nets for ... 😄

[jankurianski]

Ahh, thanks @jornh ... looks like I just missed out on 4b27600 from master

[amaitland]

@jankurianski Fantastic! Thanks 👍

I have ensured everything works in Debug/Release and x86/x64 mode, however I am unsure about the nuget packages as I don't know how to build them (and was hoping someone else could tell me if it works 😉).

No problem, I can sort the nuget packages out (unless @jornh beats me to it 😄)