[widgets][dialogs] Make new dialog comboboxes searchable

This patch makes the combo boxes editable so the user
can start typing what he is looking for rather than
having to scroll a possibly long list of assets.

Fixes #227

beat/editor/widgets/dialogs.py

@@ -120,6 +120,16 @@ class AssetCreationDialog(QDialog, CreationType):
         button_group.addButton(self.new_version_radio_button)
         button_group.addButton(self.fork_radio_button)
 
+        # Combo boxes setup:
+        for combobox in [
+            self.toolchain_combobox,
+            self.new_version_combobox,
+            self.fork_combobox,
+        ]:
+            if combobox:
+                combobox.setEditable(True)
+                combobox.setInsertPolicy(QComboBox.NoInsert)
+
         # Layouts
         fork_layout = QVBoxLayout()
         fork_layout.addWidget(self.fork_combobox)