Review and refactor function StructsFromRows()...

[chebrolus]

...
for better readability/maintainability and to confirm to gocyclo complexity

[haomingzhang]

In most cases, callers should call db.QueryStructs instead of calling StructsFromRows directly. However, it's useful in the cases that the caller is not using apid.Db.
I can add examples on the usage of StructsFromRows in func description, as well as gocyclo complexity. Do you have specific improvements in mind?