refactor(compiler): add createAotCompiler factory

Also adds 2 more methods to the `AotCompilerHost`:
- `loadResource`
- `resolveFileToImport`

modules/@angular/compiler/test/aot/static_reflector_spec.ts

@@ -511,6 +511,12 @@ class MockAotCompilerHost implements AotCompilerHost {
 
   constructor() {}
 
+  loadResource(filePath: string): Promise<string> { throw new Error('Should not be called!'); }
+
+  resolveFileToImport(importedFilePath: string, containingFilePath: string): string {
+    throw new Error('Should not be called!');
+  }
+
   // In tests, assume that symbols are not re-exported
   resolveImportToFile(modulePath: string, containingFile?: string): string {
     function splitPath(path: string): string[] { return path.split(/\/|\\/g); }