Completion fixes

Cleaning up some rough edges with completion list:
* completion on call/new expressions
* completions in type positions
* completions on module exports
* filtering private member completions based on location
* disable completion list in with blocks
* completion for object literal property names based on contextual type
* completions before keywords

There changes were driven by tests, so tests were all enabled in the beginning. sorry if this makes it harder to review changes.

calling lookAhead(... isREservedWord) doesn't seem right.  It missed hte simple case of:

```
name.
class C
```

C is not a reserved word, it is just an identifier