Clean up main.cpp and add CRC8

[laura-ebs]

• [x] Make classes for CRC8 data error correction code (ECC)
• [x] Make classes for the sensors
• [x] Remove unceccesary code in main
• [x] Test and verify that it works

The last part I tried to do however I couldn't find the problem, hopefully someone will be able to help me with this.

[laura-ebs]

I verified that the code works, we do not need CRC8, because TTN already has it own built in CRC8