As Hippo, I want the list of available Essentials plugins to be served over the internet

Currently, this list is more or less hardcoded into Essentials. When Hippo publishes an updated list of components, the list that a developer sees in Essentials must be updated the next time he opens the "Add components" tab - so without rebuilding the app!

It must be possible to update the list without involvement from infra.

Demo can be as simple as:

• Start Essentials, see that the list is empty
• Update the file, adding the content blocks plugin
• Open the list again, see that the content blocks are there and install it

This feature is accepted if:

• the list of plugin descriptors can be retrieved dynamically from external sources.
• the dashboard reports appropriate feedback when external resources are unavailable
• a plugin (dashboard and/or hippo) can be used in the dashboard, which the corresponding artifacts reside in a third-party maven repository (i.e.: add repository to project POM, demo that such a plugin can be used successfully).