Updated the ADC TEP once more:

Updated the ADC TEP once more:
1) integrated last suggested by reviewer (J.Stankovic):
 - added a subsection in the "Implementation" section to reference the "TestAdc" implementation
 - added a section that better describes how the "AdcConfigure" interface pulls the client's settings
 - "sensors" -> "sensor drivers" in the introduction section
2) documented the ReadNow interface - as agreed during the last confcall it will not be documented in the SIDs TEP
3) minor (cosmetic) changes