Hooks menu items to import/export methods. Refs #15.
Attempts to build an ownerless progress sheet. Refs #15.
Adds new EHProgress_vc to control animation. Refs #15.
Asks user for type of importation. Refs #15.
Implements importation. Refs #15.
Implements exportation of csv file. Refs #15.
Improves csv exportation suggested filename. Refs #15.
Implements csv file dragging over app window. Refs #15.
Adds csv file dragging on dock icon. Refs #15.
Handles modal sheets during icon csv importation. Refs #15.
Mentions CSV import/export in embedded help. Refs #15.
Documents task in changes log. Refs #15.
Merge branch 'feature/t15_add_csv_import_export'