WIP: admin job edit - add items
Refactor handling of temporary jobs
Fix labour spec
Merge branch 'master' into admin_job_edit
Fix labour duration handling
Harden job items validation, add client-side validation, minor fixes
* Add support for adding tasks to job
* Fix adding task items
* Fix task total calculation
Merge branch 'master' into admin_job_edit
Improve job editing
Merge branch 'master' into admin_job_edit

Conflicts:
	app/models/jobs/job.rb
	db/schema.rb
	spec/models/jobs/job_spec.rb
Fix ajax calls to request json data
More json fixes
Fix whitespace
Fix job edit spec, fix task editing
Merge branch 'master' into admin_job_edit
* Add ServiceCost task item
* Refactor job total calculation
Cosmetic fixes
Fix total calculation bug
Improve service task editing
Restrict ServiceCost item deletion