Primary key detection is not used (in particular, by foreign key detection)

[ZhuofanXie]

As detailed in the project description paper https://dspace.mit.edu/handle/1721.1/127410, foreign key detection should take primary key detection's outputs as arguments. But it is not so in the current version.

[ZhuofanXie]

Could have FKD take in PKD's predictions and only look at column pairs in which at least one is a primary key