InputData: make the tuple investigation more resiliant to an edge case
InputData::Find<InputDataNS::Restart>
fails currently in the input data tuple is defined using solely its elements.
To make it plainly, if the tuple is defined with
<...
InputDataNS::Restart::::TimeIndex,
InputDataNS::Restart::DataDirectory,
...
>
Restart
section won't be found. It won't matter most of the time as it is much more natural to define it instead with
<...
InputDataNS::Restart,
...
>
but it should nonetheless work with both choices.