sbus: add a{sas} get invoker Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

sbus: use hard coded getters instead of generated Properties are single value of a small number of predefined D-Bus types. There is no need to generate them with codegen. Actually, the source generator for property getters is already quite mess with branching for array, strings and object paths. Adding any more complex type in the future (such as dictionary) would require even more branching or creating a separate path for it. Hard coding the getters will simplify creating new ones for more complex types. This patch also reduces lots of code duplication and creates a simple function for GetAll. Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>