Fix for device deletion

[JahleelAbraham]

This PR contains a change in structure for the DELETE /devices/{id} route.

Despite it passing tests, it presented some issues on some Bluecherry deployments. With the help of DTV, the approach was changed to a promise chain, this will ensure that the records in the database are properly disposed of before moving to delete the main device record.

Along side this fix, there are minor spelling corrections and code formatting tweaks.

[andrey-utkin]

I request that you...

• add a test which would reproduce the problem you're targeting here, so that in future we could change the code again and not do as much thorough manual testing. As this is a timing problem, there are two approaches possible:
  • stress-test, repeatedly hammer it with a high count of repetitions which would ensure the old version of code hits the problem;
  • instrument the product code with some "internal_test_delay" hidden parameter (ideally not affecting the user-visible API) to insert a long delay into a deletion process, so that we could insert a Media entry in the test code so that delete operation fails.
• Leave the old, non-repeated function available (ideally as an organic part of your looped logic): as soon as the schema change allowing cascade delete db: Allow DELETE FROM Devices, cascade Media and EventsCam bluecherry-apps#696 is released, the more complex repeat loop can be dropped, let's make it convenient to drop it.
• Restructure the code to avoid such deep code nesting. So many braces! There are no obvious mistakes, but I can't really say I could follow the logic of the code. I understand that JS dictates some of that, asynchrony dictates some of that, and part of the problem is my unfamiliarity, but still I request you try as I believe some improvement on readability by reduction of nesting should be possible.