add LMS plugins and Material skin in base image

[gorski123]

Can we configure LMS in our factory image to include the standard plugins most would want (Spotify, Pandora, Tune-in, Tidal, Airplay, etc). Can we also default LMS to use the Material skin (https://github.com/CDrummond/lms-material) as opposed to the old school looking interface for the web interface?

[gorski123]

Here is a list of the LMS plugins that need to get installed on the LMS server. Note this is subject to change.

[rtertiaer]

blocked on #599