Don't override project file settings right after loading them

This fixes a bug which was introduced during the SQLCipher development
and which caused some settings loaded from a project file to be loaded
but then replaced by the default values which were loaded right
afterwards.
Parse and save foreign key constraints

When parsing a CREATE TABLE statement read and try to parse any foreign
key constraints and save that information.
tests: Add tests for foreign key parsing
Add column to EditTableDialog to allow setting foreign key constraints

Add a new column to the fiel table in the Edit Table Dialog to allow the
user to add and edit foreign key constraints.