App Layout: Update Tabler dependency, revamp layout

[earboxer]

This is a replacement for #54

To test this, npm install && npm run gulp in this project, you may also need to run php artisan otter:install in your main project.

This PR simplifies the stylesheets: No more SCSS!!! Tabler now supports dark themes, so we don't need to add any of our own code.

This changes the layout to use CSS Grid (rather than the mix of bootstrap and tabler class names).

This changes the navigation menu to use blade to create it in blade instead of in vue. (it also only appears once in the DOM instead of twice). It is not hidden behind a hamburger menu anymore for small screens).
You should test this to make sure it works: I don't have any nested menus, so it may not work with those.

With the node update, some things changed, some of which are commented out:

• updated trumbowyg (You should test this out, I have not tested it!)
• sparkline and circle-progress are not distributed the same way in the new version of tabler: I'm not sure if this means we have a problem, we're including tabler.js (instead of their old core file, so maybe it is included?).
• feather webfont is no longer distributed by tabler... do we need this? (maybe we should uncommit it from our /public folder when we compile the assets)

[earboxer]

I pushed it without the compiled files. Line-wise, the biggest change is package-lock.json ... ugh NPM.