Add doxygen documentation to connman_service code and header file

Open-webOS-DCO-1.0-Signed-off-by: Sapna Todwal <sapna.todwal@palm.com>

Change-Id: I8878dcad818e111545ed192a11328306d0560ba9
Reviewed-on: http://g2g.palm.com/1320
Tested-by: Sapna Todwal <sapna.todwal@palm.com>
Reviewed-by: Keith Derrick <keith.derrick@palm.com>