Support nulls first/last option for sorting order of custom queries
A lot of RDBMS has support for placement of null values at the start or end using options nulls first/last.
Atached patch adds two more order options to the saved query:
- Ascending nulls last.
- Descending nulls first.
And the result of issues sorted by
due date ascending nulls last:
Patch probably broken when using MySql since it doesn't have a straightforward syntax for order predicate but it's fine using SQLite3 or Postgres.