Building Succesfully in .NetCore squashed

[WIP] Initial dev workflow work

Adding init-tools.sh

Fixing issues so that corefx build in .NetCore msbuild

Port Microsoft.DotNet.Build.Tasks to NetCore

Also removed unused targets like GitPush, GitTag, ResolveNuGetPackages

Incorporate feedback comments

More Pallavi's CR feedback

PR feedback

Building corefx in NetCore msbuild succesfully