Updates sql-query dependency to 0.0.18 (adds DISTINCT function)
Moves generation of aggregation function alias to builder
Adds aggregate .as() to define alias to previous function (#123)

Usually, when using .avg('age'), ORM will define an alias called
avg_age to the returned value. If you want to change this do
.avg('age').as('my_age').
Adds DISTINCT function to all drivers (#123)