Add cancel button in manual merge

[StellaCh]

As a user, when I manually merge 2 records, I'd like to have the option to cancel the merging.

• Add a cancel button, before the Undo button (same button as in the Preview screen)
• Rename the 'Save' button to 'Merge' to make the action more clear.

[harunurhan]

After manual merge it's actually regular workflow object editing. So it would be better not mess up common ui of workflow object editing.

For cancelling, browser back should work. Although currently this won't delete created workflow
object, the real record will be untouched.