Update to new agile board API

[maartenba]

The agile board API has been removed in YouTrack 2018.2. Users on previous versions will still be able to use it, but the API will always return 404 errors on YouTrack 2018.2 and above.

When new API is available, update library to make use of it.

[NielsPilgaard]

Is there any update on this issue? Being able to work with Agile Boards through YouTrackSharp would be very beneficial to me.

[maartenba]

Right now, no news here, sorry.

The new API should be available in case you want to work around it for now https://www.jetbrains.com/help/youtrack/standalone/resource-api-agiles.html

[NielsPilgaard]

No worries, I'll use the API for now as you suggest.

Thanks for the quick response!

[timgaunt]

Are there any plans to support the new API? It looks as though there's a PR ready. Would be good to get it in place: #103