device packages: depend on postmarketos-base

Created by: ollieparanoid

• Add postmarketos-base as dependency for all device-* packages (current and new ones generated with aportgen)
• postmarketos-base: don't source /etc/deviceinfo in post-install anymore (it was used to enable the msm-fb-refresher service depending on the deviceinfo)
• msm-fb-refresher: enable the service in post-install
• Add a test case to test/test_aports_deviceinfo.py and rename it to test/test_aports.py

This is required for #1247 "Don't mark all packages as explicitly installed" (see also: the discussion in that thread).