Add kvm and dnvm (ASP.NET vNext command line tools)

* kvm is the current version that may be deprecated soon
* dnvm is the new version that is still in heavy development

They may not play well together, but they both work individually.

dnvm.json

@@ -0,0 +1,13 @@
+{
+    "version":  "latest",
+    "license":  "Apache 2.0",
+    "url":  [
+        "https://raw.githubusercontent.com/aspnet/Home/dev/dnvm.ps1"
+    ],
+    "homepage":  "https://github.com/aspnet/Home",
+    "env_set": { 
+        "DNX_HOME": "$dir\\.dnx",
+        "DNX_USER_HOME": "$dir\\.dnx"
+        },
+    "bin": "dnvm.ps1"
+}

kvm.json

@@ -0,0 +1,14 @@
+{
+    "version":  "latest",
+    "license":  "Apache 2.0",
+    "url":  [
+        "https://raw.githubusercontent.com/aspnet/Home/master/kvm.ps1"
+    ],
+    "homepage":  "https://github.com/aspnet/Home",
+    "env_set": { 
+        "KRE_HOME": "$dir\\.k",
+        "KRE_USER_HOME": "$dir\\.k" 
+        },
+    "bin": "kvm.ps1",
+    "post_install": "iex \"kvm upgrade\""
+}