Changes:
* Stop producing Microsoft.AspNetCore.Routing.DecisionTree.Sources. I could not find any usages outside of the Microsoft.AspNetCore.Routing assembly, so I've moved this to be a subfolder of code in the Microsoft.AspNetCore.Routing project.
* Stop building src/Routing as a submodule. Use ProjectReference instead
* Move projects from src/Routing into src/Http/Routing/ and src/Http/Routing.Abstractions/
* Update package baselines and dependencies to support building routing projects and samples
This changes DataProtection to build as projects instead of a pseudo-submodule. It replaces Package and ProjectReference with <Reference> items which custom targets then resolve.
* Add build definition for Azure DevOps
* Put code for metapackages in a subfolder
* Update targets to prepare for submodules merging into this repo
* Add source code for windows installer
* Add source code for Debian installers