All places in the gluon_ssid_changer source code use the type "settings"
for the main config section of the package. But the upgrade script switches
this to "main" for no obvious reason.

The gluon.site module request that the structure elements are called to get
the actual content of the string. The simple-uci will not do that and
instead cause an exception because the caller didn't provide a string.

closes #19

Siehe https://github.com/freifunk-gluon/gluon/commit/7ccdacd294e5fcb6718f806543bb2620c02c9ddb