String improvements

[Davide DB]

Sensor1
Sensor2
Sensor3

.../qt-ui/profile/diveplotdatamodel.cpp:139

Shouln't be "Sensor 1" "Sensor 2" "Sensor 3"?

Sorry to be nitpick but this morning I realized I'm translating over
and over the same strings.

Moreover Transifex could be really useful if translators could see
where suggestions (strings suggested) come from.
This morning I found 54 string to translate but 90% of them where
already translated in the past.
It's a mystery to me if are all of them are duplicated or it has some
sort of cache...