Update actions list when selected active file updates

[duranb]

Resolves #1821

To test:

1. Create a workspace
2. Upload an action that has a file or sequence type parameter
3. Create a sequence file in the workspace
4. Navigate to that file if not already
5. Copy the link to this page
6. Paste into a new browser window
7. Confirm that the Actions dropdown above the sequence editor is clickable.