[BUG] Loading studies is slow

[IvoTod]

What happened:
When loading studies in duckdb2, loading the family data is incredibly slow. The 3 slowest parts are the pandas.DataFrame.to_dict call, the FamiliesData redefine method and the Person redefine method, which gets called on every Person object created. Each of these 3 parts takes 15-20 seconds, adding up to an entire minute of load time.

What you expected to happen:
It should be possible to reduce the loading time drastically, so that starting the GPF system is much faster.

Attached are results from profiling, sorted by cumulative time. The second file is with the to_dict call replaced with manual iteration.

profiling1.txt
profiling2.txt