Move admintable vue component to its own package

[nfourtythree]

Description

Currently, all the Vue related things for the admin table are located in the admintable asset bundle. This works perfectly fine if you are using it as part of a template or maybe even if you are instantiating it from another piece of JS.

In both of those cases calling new Craft.VueAdminTable({ ... }) will get you what you need.

From a plugin's perspective, the problem (that this PR looks to solve) arises when you are using Vue and would like to use the component inside your app. At this point you have two options, either instantiate it with the normal JS method (losing out on being able to hook into the Vue "goodness") or include it by having the cms repo checked out and having a long-winded relative path on the import (e.g. ../../../../../../cms/src/web/assets/admintable/App.vue).

Neither are particularly ideal, but moving it to its own package means it is easily includable both from within cms and for plugin developers.

This PR gives scope to also have further components in the future. For example Commerce had a need to recreate the HTML for a field in a Vue file. This could easily be moved to this new package and be available for the cms and everyone else.

The package will be publish to npm in the same way we deal with the webpack and sass packages.

/cc @timkelty

[timkelty]

Love it.