added class for TEC

Squashed all commits, removed lots of formatting changes
import struct, setpoint at -15 °C
fixed TEC, now working perfectly
cosmetic changes
added little programm for testing the TEC
- setting TEC setpoint is now working properly
- set default setpoint to -17 which should lead to a TEC temperature of about -15
decided for "struct.pack('<h', int(-5.0 * 10)) --> '0xCEFF'" for setting the TEC setpoint
Merge pull request #3 from sdickreuter/qe65xxx-tec

Qe65xxx tec
Merge branch 'qe65xxx-tec'