Run html-beautify on html files

No logic changes in the code.
$ html-beautify --version
1.4.2
$ html-beautify temperature_plot.htm > temperature_plot.htm.new
$ html-beautify temperature_log.htm > temperature_log.htm.new
$ mv temperature_plot.htm.new temperature_plot.htm
$ mv temperature_log.htm.new temperature_log.htm
Add support for multiple remote sensors

It brings support for multiple remote sensors configured in database.
Local sensor support is not changed (sensor_id=0 is used for local sensor).