Allow query sql to be defined in a file

[toddwh50]

Is your feature request related to a problem? Please describe.
Many of my queries are long and complex, making the config.yml very long. Since I don't have permission to add views or stored procedures to the target database, I cannot shorten the sql statement that goes into the config.

Describe the solution you'd like
It would be helpful to allow a query to reference a filename containing the sql for the query instead of having to put the entire sql within the YAML.

Describe alternatives you've considered
An alternative might be to implement and "!include" directive in the yaml parser that could be used to include files containing the SQL.

Additional context
None.