Split catalog_export out of editor_tools

Code, locale and test suites moved from editor_tools; docs in seven languages
with screenshots where the window has something to show; own cover.

locale/ui_en.properties

@@ -0,0 +1,14 @@
+tools/catalog_export/hint = The archive and hashes are computed on export; the JSON is written next to the mod archive
+tools/catalog_export/mod_info = Mod
+tools/catalog_export/id = ID
+tools/catalog_export/name = Name
+tools/catalog_export/metadata = Catalog
+tools/catalog_export/locales = Localizations
+tools/catalog_export/locales_hint = With no rows the English name and description of the manifest are used.
+tools/catalog_export/remove_locale = Remove language
+tools/catalog_export/preview = Resulting JSON
+tools/catalog_export/copied = JSON copied to the clipboard.
+tools/catalog_export/export_tip = Build the archive, compute hashes and write the catalog entry JSON
+tools/catalog_export/exported = Exported: {0}
+tools/catalog_export/export_error = Export error
+tools/catalog_export/url_required = Set the download URL — a catalog entry is useless without it.