As already done with other config mode texts, the altitude field now has
default texts that are used when they are not set in the site i18n files.
The altitude-help text has been removed from site i18n; instead, the
geo-location-help text now overrides the whole section description
including the part that mentions the altitude.

[Matthias Schiffer: slightly clean up code]

This was introduced in ffhh-packages at https://github.com/freifunkhamburg/ffhh-packages/tree/master/gluon-config-mode-reboot-ffhh