Recursively traverse nominated GitLab directories for reports

Back ground: Work supporting access to GitHub repositories, has been implemented as part of work done in UILDP-17, and

Similar functionality is wanted for access to GitLab repositories. The templated queries, i.e. reports, that are available to the Reporting app are specified by a set of directories within GitLab repositories. This set is maintained as part of the app's settings (UILDP-97).

Templated queries (files whose names end with .sql, accompanied by metadata in correspondingly named files with a .json extension).

These directories are currently accessed directly, but we want to recursively traverse them to gather queries found their subdirectories.