Parse list

This PR adds support for `LIST` queries to the InfluxQL parser.
I can see why you had a `parseOrderBy()` now. It does get pretty repetitive having this same block in each of the `LIST` statement functions. I'm cool if you want to move this back into a function that returns `SortFields`:

```
func (p *Parser) parseOrderBy() (SortFields, error) 
```