Specify conffiles for our packages, so they aren't overwritten during
opkg updates. While this only matters during development, it is
unintended to have different behaviour for opkg update and full firmware
updates.

gluon-announced and gluon-announce are merged to gluon-respondd.

"gluon-node-info": add section system and option role; add announce script to announce the role as nodeinfo;
add invariant script "001-node-system" to add section "system" if not exist; add invariant script "010-node-role"
to add section "system" if not exist; add invariant script "010-node-role" to set role to default value
(site.roles.default) if not exist; depends on new site.conf section