use network-manager instead of connman

connman does not work probably and i havent found out why yet (havent searched that much).
a short test and comparison shows up, that the memory consumption of both is close to identical.

So I choose now network-manager, which is much more common and comes with a much better support and feature set.

install_base/install_base.sh

@@ -133,10 +133,8 @@ apt install -y --no-install-recommends \
 message "install nanodesk base packages with recommends"
 apt install -y \
   grub-pc \
-  connman \
-  connman-ui \
-  connman-gtk \
-  connman-vpn \
+  network-manager \
+  network-manager-gnome \
   net-tools \
   isc-dhcp-client \
   host \