Added lubuntu-grub-theme and fonts

Summary: Added lubuntu-grub-theme and xfonts-efont-unicode

Test Plan: Check if lubuntu-grub-theme gets installed and selected automatically on a fresh installation.

Reviewers: kc2bez, tsimonq2, wxl, rikmills

Reviewed By: kc2bez, wxl

Differential Revision: https://phab.lubuntu.me/D68