[Developer] Lexical model compiler should type check the .model.ts file.

Currently, semantically invalid files can be passed through the lexical model compiler. As long as the TypeScript compiler can make sense of the syntax, it passes the file through.

This behaviour should be changed such that the `.model.ts` file is checked for correct types, and good diagnostic messages are given when there are type errors in the file.

Here are some options that can be passed as compiler options:

```typescript
let compilerOptions = {
project: null,
// Do not include default library file.
noLib: true,
// Only support the following libraries in the environment of the source code
lib: ['ES5', 'ES6'],
};
```

I labeled this as both `bug` and `enhancement`, because it can be considered both! 😄