Add confXXX() functions

Add a set of functions to mirror the iniXXX() functions but for regular
config files (without '[xxx]' sections headers).

Change-Id: If61630e644869662f85c2ae9be90f800dd463a56
Merge branch 'conf-functions' into dt-test
Merge branch 'test-service-functions' into dt-test
Merge branch 'update-usb-tools' into dt-test