Fix warnings in project.json

PR #2493 introduced the new project.json schema. The tree has 118 files
with the old schema, which added several hundred warnings.

This change can't go in until PR #2864 does - it relies on those bug
fixes.

TestAssets/TestProjects/PortableTests/PortableApp/project.json

@@ -1,5 +1,5 @@
 {
-  "compilationOptions": {
+  "buildOptions": {
     "emitEntryPoint": true
   },
   "dependencies": {},
@@ -24,4 +24,4 @@
       "someProperty": "someValue"
     }
   }
-}
+}

TestAssets/TestProjects/PortableTests/PortableAppCompilationContext/project.json

@@ -1,5 +1,5 @@
 {
-  "compilationOptions": {
+  "buildOptions": {
     "emitEntryPoint": true,
     "preserveCompilationContext": true
   },
@@ -16,4 +16,4 @@
       }
     }
   }
-}
+}

TestAssets/TestProjects/PortableTests/PortableAppWithIntentionalManagedDowngrade/project.json

@@ -1,5 +1,5 @@
 {
-  "compilationOptions": {
+  "buildOptions": {
     "emitEntryPoint": true
   },
   "dependencies": {},
@@ -11,8 +11,8 @@
           "version": "1.0.0-rc3-*"
         },
         "System.Linq": "4.0.0"
-      }, 
+      },
       "imports": "dnxcore50"
     }
   }
-}
+}

TestAssets/TestProjects/PortableTests/PortableAppWithNative/project.json

@@ -1,5 +1,5 @@
 {
-  "compilationOptions": {
+  "buildOptions": {
     "emitEntryPoint": true
   },
   "frameworks": {
@@ -14,4 +14,4 @@
       "imports": "dnxcore50"
     }
   }
-}
+}

TestAssets/TestProjects/PortableTests/StandaloneApp/project.json

@@ -1,5 +1,5 @@
 {
-  "compilationOptions": {
+  "buildOptions": {
     "emitEntryPoint": true
   },
   "frameworks": {
@@ -30,4 +30,4 @@
       "someProperty": "someValue"
     }
   }
-}
+}