Install librem5-base-defaults early

This makes sure e.g. apt config is in place to not fetch too new webkit. Fresh install looks like

# apt policy libwebkit2gtk-4.0-37
libwebkit2gtk-4.0-37:
  Installed: 2.30.4-1pureos0.1
  Candidate: 2.30.4-1pureos0.1
  Version table:
     2.30.5-1~deb10u1 90
        500 https://repo.pureos.net/pureos amber-security/main arm64 Packages
 *** 2.30.4-1pureos0.1 500
        500 https://repo.pureos.net/pureos amber-phone/main arm64 Packages
        100 /var/lib/dpkg/status
     2.28.4-1~deb10u1 90
        500 https://repo.pureos.net/pureos amber/main arm64 Packages

and for the pkg removal part:

# dpkg -s rsyslog
Package: rsyslog
Status: deinstall ok config-files
Priority: important
Section: admin
Installed-Size: 1707
Maintainer: Michael Biebl <biebl@debian.org>
Architecture: arm64
Version: 8.1901.0-1
Config-Version: 8.1901.0-1

Closes: #61 (closed)