Update set/get functions to follow common name scheme:
- get function have same name as in struct preferences
- set function have set_<name in struct preferences>
- signal function have <name in struct preferences>_changed
one class one .h/.cpp is the C++ idiom. Having load/sync of each
variable in 1 functions (in contrast to the distributed way SettingsObjectWrapper
handles it) secures the same storage name is used. Having the set/get/load/sync
functions grouped together makes it easier to get an overview.
REMARK: this commit only defines the class, it is not active in production
Signed-off-by: Jan Iversen <jani@apache.org>
