Fixes a number of small bugs in the Drippie management script.

- Fixes a bug that caused Gelato tasks to be created with the
wrong time interval.
- Improves the Drippie script to correctly pause tasks that are
no longer present in the config file.
- Adds config file prefixing so that the management script can
be used with a number of different config files without those
other tasks being paused by accident.