Resolve "FlexDelft export improvements"

Continuation of !395 (merged) Closes #190

Edits the following pages: applications/all, applications/all/flexdelft and declarations/all

• In each page I added a "Search" button for simplifications/less JS and less reloading every time the user changes something.
• The exports now have filters for periods in all these pages
• Added the program name in the exports (following what Timur did)