refactor(compiler): add createAotCompiler factory

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

modules/@angular/compiler/index.ts

@@ -25,6 +25,7 @@ export * from './src/template_parser/template_ast';
 export {TEMPLATE_TRANSFORMS} from './src/template_parser/template_parser';
 export {CompilerConfig, RenderTypes} from './src/config';
 export * from './src/compile_metadata';
+export * from './src/aot/compiler_factory';
 export * from './src/aot/compiler';
 export * from './src/aot/compiler_host';
 export * from './src/aot/static_reflector';