Unify Command and Operation status codes.

[mihakrajnc]

We need to unify status codes that get return in status listeners (OperationObserver, CommandResult...), and use those status codes in all public calls.

Something like:

@IntDef({CommandStatus.SERVICE_NOT_FOUND, CommandStatus.CHARACTERISTIC_NOT_FOUND, CommandStatus.DESCRIPTOR_NOT_FOUND})
public @interface CommandStatus {
    int SERVICE_NOT_FOUND = 0;
    int CHARACTERISTIC_NOT_FOUND = 1;
    int DESCRIPTOR_NOT_FOUND = 2;
}