[Feature] Sync Features from Client Repo (#425)

- New PackageImporter
- Fix persisting Molfile on Structure creation
- Add NonPersistent Prediction
- Pathway View Options
- Edit Node Fix

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#425

epdb/exceptions.py

@@ -4,3 +4,7 @@ class InvalidSMILESException(Exception):
 
 class InvalidMolfileException(Exception):
     pass
+
+
+class PackageImportException(Exception):
+    pass