InfluxQL cheat sheet

Originally: https://github.com/influxdb/influxdb.com/issues/359

List all queries with their full syntax, in alphabetical order.

https://github.com/influxdb/influxdb/blob/master/influxql/INFLUXQL.md has the list of all queries and a lot of the syntax, but it needs to be simplified and we need to make some of the syntax more explicit, e.g. what can accept regex operators and what cannot.
