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.

Can you do `lookAhead(scanner.isReservedWord)`?