Fix the project.json for C# library and add tests (#3507)

* Fix the project.json for C# library and add tests

This commit fixes the bug introduced in project.json for the C# Library
template. It also adds two simple tests for the library template that
drop the class library and then restore and another that also builds.

Fixes #3496

src/dotnet/commands/dotnet-new/CSharp_Lib/project.json.template

@@ -7,7 +7,9 @@
   },
   "frameworks": {
     "netstandard1.6": {
-      "NETStandard.Library": "1.5.0-rc3-24126-00"
+      "dependencies": {
+        "NETStandard.Library": "1.6.0-rc3-24210-06"
+      }
     }
   }
 }

src/dotnet/commands/dotnet-new/README.md

@@ -29,7 +29,16 @@ Language of project. Defaults to `C##`. Also `csharp` ( `fsharp` ) or `cs` ( `fs
 
 `-t`, `--type`
 
-Type of the project. Valid values are "console" and "web".
+Type of the project. Valid values for C# are:
+
+* `console`
+* `web`
+* `lib`
+* `xunittest`
+
+Valid values for F# are:
+
+* `console`
 
 ## EXAMPLES