Cleanup nPo_Trend.php File
Provide a proper method for utf8 escape

I have a Problem with utf8 on '°C'. It will provide nothing on trend
file.
With this solution we escaping  $value[Tag_Unit] in array() before
rendering it with mustache. Such a workaround solution.
Is this possible with an Helper fonction on mustache Engine? I couldn't
make that work.