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/tests/mod.rs

@@ -17,6 +17,7 @@ mod asking;
 mod codes;
 mod notices;
 mod numbers;
+mod transfer;
 
 struct Stage {
     root: FocusHandle,