Drupal 8 port

I try to make a working version of the module for drupal 8.
The main functions work already.

This patch is true

Thanks for the patch, this has been applied to the dev branch

Great! I will add new changes here if there will be.

Changelog:
- Removed QueueWorker;
- Fixed "periodic" value save;
- Fixed a period to dispatch scheduled jobs;
- Fixed an info for log;
- Added the ability to create queues and to set a worker callback.

The new patch has been applied to the dev branch

Changelog:
- Fixed records updating in the database. Before: A new record was creating, if it did not exist.

Again, this patch has been applied to the dev branch

Changelog:
- Logger adds information if there is one;
- Replaced the invoking queues. Added the derivative and the queue worker. Now it compatible with the queue_ui module;
- Changed API documentation for hooks.

And.. it's all. I a lot of time thinked about realize queues, but I decided to leave everything as it is (from D7). If you have any ideas how to improve the module, then I will be glad if help is provided. For example, refactoring and writing documentation.
I think this module is almost finished.
Thanks.

Applied the codesniffer_fixes.patch

Once again thanks m.lebedev for your work on the port, if you think the module is almost finished then is it time to create an alpha/beta release?

I think any new features/improvements should be handled in separate issues so we can get this port out ASAP. The test bot will always fail as there is no test coverage and to my mind would be the only release blocker.

@Francewhoa you initially stated:

We would be happy to contribute testing patch, quality assurance, documentation, and agile project management services if needed

If this is still on offer then I think now would be the time for this to kick in.

I think that we can wait about 2 weeks and after that to create an alpha release.
I use this module in my project now. I will report here about errors of the module if they occur. If not, then release!

I have added some very simple tests (taken from Drupal 8: Writing Your First Unit Test With PHPUnit) which will hopefully satisfy the testbot and can be added to as necessary.

Looking at current interface \Drupal\job_scheduler\JobSchedulerInterface it require better naming for methods then it makes sense to implement unittest for \Drupal\job_scheduler\JobScheduler

Is time to create an alpha release?

Alpha release has been created and this issue marked as Fixed.

Any bugs can reported separately to this issue, thanks for all your help