TMSS-241: remove units from resource models (which should always be in SI/base units on the DB level)

Resolve TMSS-152

Closes TMSS-152

See merge request !180

TMSS-152: refactored observation task->subtask specification conversion, so it's more generic, and easier to read.

TMSS-152: added test_create_task_blueprints_and_subtasks_subtasks_from_scheduling_unit_draft_with_UC1_requirements

TMSS-152: made sure that create_task_drafts_from_scheduling_unit_draft is always called when processing specification in scheduling_unit_draft. Check and skip already created task_drafts and/or relations

Resolve TMSS-189 (and TMSS-192)

Closes TMSS-189

See merge request !182