Fix cross-env binary

[5.4] Use consistent config paths

[5.4] Fix cross-env bin path

[5.4] Update description of filled rule

`filled` isn't really required. It just implies that it needs a value.

Refactor npm scripts

Per #4147, this adds a new `npm run watch-poll` command, and dries up some of those long repetitive commands.

Change hard-coded '/login' param to named route

Update package.json

update laravel mix to new version

Updated axios, jQuery, Laravel Mix, Lodash and Vue.js versions

Add font path variable

Apply fixes from StyleCI

Updated laravel-mix version

Laravel 5.4 explicitly require phpunit 5.7.0+

As demonstrated in laravel/framework#17699 it is possible to have phpunit being installed with a lower than `5.7.0`, which doesn't work at all on 5.4 due to the changes with PHPUnit namespaced class.

Add App locale as default value of 'lang' attribute

Add App locate as default lang in the app.php config file instead of 'en' of 'lang' attribute in the main view.

Revert "Append '@' to let composer resolve PHP executable"

Make Axios automatically send `X-CSRF-TOKEN` in the header

Append '@' to let composer resolve PHP executable