Preferences should more logical

[adrianbroher]

The current layout of the preferences dialog has grown over time without rethinking the visual impact. Grouping the settings by

• General settings
  • Sensor polling
  • Temperature unit
• Panel related settings
  • Sensor showed in the panel
  • Sensor
• Display related settings
  • Display temperature, fan speed and/or voltage
  • Display drive temperatures

could make the preference a lot less cluttered.

Also the widgets should be better chosen and the behavior should be more consistent:

• The temperature units should be a drop down menu.
• The drive temperature slider should be only enabled if hddtemp is actually installed.
• The 'Show sensor label' should be a slider too.