Save & Add New + Save & Duplicate

Many people prefer to not have to go back to the list view and click again to add a new item. Additionally, for example in cars, you may have several cars of different years and you want to duplicate most of the info, but change a couple of fields. These changes add that functionality

NOTES: 
You have to use a manual hidden id field since C5's form helper overrides it with the post variable (submitting a pull request for a fix for this to the C5 core soon)
The buttons were changed to the form instead of interface button style since they needed different names. Formatting was left intact