Change way to find signals to make it a little bit more generic.

Change way to find signals to make it a little bit more generic.

Now we have basically 3 functions :
 - one for subscription which return signal name into a vector
 - one to find from CanSignal vector
 - a last to find from Obd2Pid vector

Name of some function has been changed.

May be reworked later.

Change-Id: Ie72969fd20503fc1f9291958dc2ac5d827a6be59
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>