[3.0] Rename asset command to publish

[dwightwatson]

I noticed that Horizon is the odd one out when it comes to the naming the command to re-publish assets.

roomies git:(master) ✗ php artisan | grep publish
  horizon:assets       Re-publish the Horizon assets
  nova:publish         Publish all of the Nova resources
  telescope:publish    Publish all of the Telescope resources
  vendor:publish       Publish any publishable assets from vendor packages

This simply updates the command to match - horizon:publish.

In addition it adjusts the order of commands in the service provider - the bottom half appeared to be alphabetical but the top half was not, so I made it all alphabetical.

[taylorotwell]

I think this would technically need to go to master branch.