Rename "dotnet" to "NETStandard"

Fixes https://github.com/dotnet/corefx/issues/5707

We are changing the .NET packages to no longer use the ‘dotnet’, ‘dotnet5.x’, and ‘dnxcore50’ monikers.  This is thee first stage of the change for dotnet->netstandard.

The replacements are as follows

Old moniker | New moniker
----------------- | ------------------
dotnet5.x | netstandard1.y  (where y = x -1)
DNXCore50 | netstandardapp1.5
dotnet | netstandard1.3

To prepare for this change you can do the following to your project.json.  This change will require a recent build of NuGet or dotnet.exe and can be done prior to consuming the packages with the breaking change.  These packages will not work with DNX.

For a project targeting dotnet5.6
```
    "frameworks": {
        "netstandard1.5": {
            "imports": [ "dotnet5.6" ]
        }
    },
```

For a project targeting dnxcore50
```
    "frameworks": {
        "netstandardapp1.5": {
            "imports": [ "dnxcore50", "portable-net45+win8" ]
        }
    },
```

[tfs-changeset: 1578321]

1 files changed, 5 insertions, 0 deletions

diff --git a/Packaging.props b/Packaging.props
index 2fbadfe3d0..1ed8694ea3 100644
--- a/Packaging.props
+++ b/Packaging.props
@@ -12,6 +12,11 @@
     <PackagePlatform Condition="'$(PackagePlatform)' == ''">$(Platform)</PackagePlatform>
     <PackagePlatform Condition="'$(PackagePlatform)' == 'amd64'">x64</PackagePlatform>
     <NativePackagePath>$(MSBuildThisFileDirectory)src/Native/pkg</NativePackagePath>
+
+    <!-- Enable NETStandard -->
+    <UseNetPlatform>false</UseNetPlatform>
+    <BaseLinePackageDependencies>true</BaseLinePackageDependencies>
+    <ExcludeRuntimeJson>true</ExcludeRuntimeJson>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(OsEnvironment)'=='Unix'">