Adding a "BranchName" branchinfo.txt variable like we have in core-setup. This allows to update the correct path under dotnet/versions/build-info.
Also, moving UpdateVersionsRepo into FinalizeBuild.
Moves CLI version suffix from preview1 to preview2
Sets channel for preview2 to 1.0.0-preview2, abandoning the Beta channel to the 1.0.0-preview1 release. Once @sokket's publishing cleanup work is complete we can re-converge the channels if desired.