Add column defaults to ORM models and tests

[maximemulder]

Week-end PR because I want to take some afternoon off next week.

This PR adds default values to the ORM models of LORIS-MRI, which allows to type check the ORM constructors by knowing which fields are required or not (this was the only hole in ORM typing currently).

The PR also update the ORM-SQL integration test to ensure that these defaults match those of the SQL definitions of LORIS main. Some of the defaults of our SQL schema look quite suspicious and should be removed IMO, but this is something that should be treated in LORIS main first if we want to fix it.

The first commit updates the SQL schema (and minor formatting that I was too lazy to add in a separate PR).
The second commit adds a SQLAlchemy decorator (I refuse to write "true" or "false" in my code !).
The third commit adds the defaults, which are checked by the previous integration tests.