New sensors support

Added three new sensors:

### Thermal sensors

For now they support only one measurement per sensor. The measurement is ideal regardless of its distance. If thermal sources exist in the measurement cone, the sensor returns the highest temperature.

### Sound sensors (microphones)

A naive approach of a microphone. The user adds sound sources in the environment and selects their intensity (Dbs). A sound sensor adds all the dbs from different sources that are in its vicinity. 

A table showing typical db values can be found here : http://en.wikipedia.org/wiki/Sound_power#Table_of_selected_sound_sources

We supposed that from 0 to 0.5m from the sound source the sound intensity is the nominal one (the one the user provides) and for larger distances it drops according to the inverse square law (http://hyperphysics.phy-astr.gsu.edu/hbase/acoustic/invsqs.html).

Problems: 
- Walls are not considered in the model
- Reflections are not considered
- The sensor returns 0 db when the source is in a greater distance than maxRange (is this correct?)

### CO2 sensors

They work in the same way as the sound sensors. We suppose that from distances from 0 to 0.5m the CO2 ppm (parts per million) have the nominal value and in larger distances the measurement follows the inverse square law. I couldn't find any mathematical model for gas diffusion from a constant gas source in an empty environment. The problems are similar to the sound sensors'.