title: Patch assembly and nuget version of each project independently
body: <p>I have a solution with multiple projects (each is a nuget package for some common utils).</p>
  
  <p>I want to build all these projects in VSTS.</p>
  
  <p>The problem each project has a unique version.</p>
  
  <ol>
  <li><code>version.txt</code> file is stored in each project's folder, and contains the version in format <code>x.x.x</code></li>
  <li>before build each project should be patched with this version</li>
  <li>build and push nuget packages</li>
  </ol>
  
  <p>VSTS contains task <code>dotnet build</code> which can build an entire solution or a concrete project. But I need to automate this process - once the new project was added it should be built automatically.</p>
  
  <p>I didn't find the ready-to-use build task which can read the file and patch all parameters of csproj (FileVersion, AssemblyVersion, Version, PackageVersion), and do this per project.</p>
  
  <p>It would be great to have this version.txt file to have a single point of configuration (instead of changing all the parameters)</p>