Align with other ASP.NET Core projects

[dougbu]

• part of #228
• use regular LICENSE.txt and Key.snk
• use BuildTools
  • start with aspnet/BuildTools/tree/dev/scripts/bootstrapper files
  • copy other files and pieces of files from aspnet/Mvc repo
  • remove properties that BuildTools sets from root Directory.Build.props
• use Internal.AspNetCore.Sdk
• update version to 1.0.0-preview1
• work around #231 (aka dotnet/standard#567)

nits:

• remove support for <Configuration>CodeAnalysis</Configuration>
• centralize references in test projects
• remove a few files I missed in #230

Aligning dependency versions (using dependencies.props) will come soon.

[dougbu]

@danroth27 / @Eilon the Readme.md file seems a bit sparse after removing the no-longer-relevant documentation links. Do we have a standard paragraph or two describing ASP.NET Core WebHooks?

[dougbu]

:up::date: to clean CI builds

[dougbu]

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