Create FK column from new column dialog

[seancolsen]

Current behavior

• If I want to create a new FK column from the UI, I have two options:
  • Use the "Create Link" dialog
  • Create a new column using the type of the target column. Then manually add an FK constraint.

Desired behavior

• I want to create a new FK column by clicking the same "+" button that I click when creating a non-fk column.

Design work

• The "New Column" form would need design changes to figure out how to get all the right information from the user.