add "SQLite." prefix in Table, Expression

[georgeef]

(This PR is the same as #10, but with MMEX.xcodeproj excluded).

After update to Xcode 16.0, I cannot compile. Seems that Foundation also defines Expression and there is a name collision. I couldn't find a way to declare in Swift that Expression must be taken from SQLite.

This PR adds the prefix SQLite. in front of Table and Expression.

Note: I also tried to remove Foundation, or to import from it only the names that are needed, effectively making SQLite the only fully imported library. It works (with less changes in the code), but I think adding an SQLite. prefix is more robust and more clean.

[georgeef]

see also stephencelis/SQLite.swift#1269. three solutions are proposed there:

• add prefix in each occurrence of Expression, as in this PR
• add typealias Expression = SQLite.Expression at file level
• add import SQLite.Expression at file level