Drupal coding standards

The patch provided in #2 no longer applies cleanly to the 8.x-1.x-dev branch and needs to be re-rolled.

The previous patch didn't apply mainly because most of the logic from the tb-megamenu-touch.js file has been rolled into tb-megamenu-frontend.js. I've re-rolled the proposed changes so the new patch applies to the 8.x-1.x-dev branch while also making further adjustments to better conform to coding standards. While technically more of a best practice than a standard I've also converted the TBMegaMenuBuilder class into a service to allow the overall module to better leverage dependency injection, and eliminated calls to \Drupal:: wherever possible.

I'm planning to re-roll the patch from #4 since we're aiming to resolve 2965871 - and potentially some of the other open Major bugs - first. Additionally, after consulting with some of the project maintainers it seemed safer to address the new service and move towards dependency injection in a separate task, which I've created here.

We are aiming for a stable release, so we are updating the priority to "Major".

Once 3183288 has been fixed the patch from #5 should be re-rolled.

I've re-rolled the patch from #5 again, ensuring it applies cleanly to the 8.x-1.x-dev branch following the completion of 3183288. When applying the patch please be sure it's against 8.x-1.x-dev, otherwise it'll fail. All functionality should be regression tested since a good portion of the module's codebase was updated to meet coding standards.

Issue has been reviewed and tested by @knaffles and myself. Everything looks good. No regression issues found.

Issue has been merged into the 8.x-1.x-dev branch. It will be a part of the next release.