Misc · Export and import: export, field mapping and a CSV importer

misc::ExportDialog offers the owner's formats as cards and hands the
chosen one over for the owner to write. misc::ImportDialog maps the
file's columns to the app's fields, matched by name to start, over a
preview, and asks for each required field's column. misc::CsvImporter
reads CSV as RFC 4180, lets the first row name the columns or not, and
maps it through the ImportDialog into records; text that does not read
says why.

src/misc/mod.rs

@@ -3,7 +3,10 @@ mod captcha;
 mod clock;
 mod consent;
 mod cookies;
+mod csv;
+mod export;
 mod flashcards;
+mod import;
 mod licenses;
 mod poll;
 mod quiz;
@@ -20,7 +23,10 @@ pub use captcha::{Captcha, CaptchaState};
 pub use clock::{Clock, WorldClock};
 pub use consent::ConsentDialog;
 pub use cookies::CookieBanner;
+pub use csv::{CsvImporter, read_csv};
+pub use export::{ExportDialog, ExportFormat};
 pub use flashcards::Flashcards;
+pub use import::{ImportDialog, ImportField};
 pub use licenses::{LicenseViewer, Package};
 pub use poll::Poll;
 pub use quiz::{Quiz, QuizQuestion};