Client file deletion

- Add file delete confirmation modal
- Change file deletes to POST not GET requests in post.php as they are state changing
- Require CSRF validation for file deletes

js/file_delete_modal.js

@@ -0,0 +1,5 @@
+function populateFileDeleteModal(file_id, file_name) {
+    // Dynamically populate the file delete modal with the file id (hidden) and name
+    document.getElementById("file_delete_id").value = file_id;
+    document.getElementById("file_delete_name").innerText = file_name;
+}