Code improvements to upgrade sig score

[robdeltares]

Kind of request

None

Enhancement description

1. Remove shared pointers for Sample and ModelSample
2. Split up ProjectHandler to separate classes for each type (leading to StochastHandler, HistogramValueHandler, etc) . They should all inherit form a templated base class

Use case

No response

Additional context

No response

[robdeltares]

Pull requests:

#356

[robdeltares]

Pull requests for split up project handler:

#359
https://github.com/Deltares/PTK/pull/100