Perforce diff generated by crucible.py doesn't include new files opened as 'branch'

Example p4 opened output:

//depot/private/ProjectY/codelines.txt#1 - branch default change (text)
//depot/private/ProjectY/codelines2.txt#1 - branch default change (text)

These don't get included in the standard perforce diff, and the additional handling for new/removed files in crucible.py doesn't include them, as it's looking for files that are 'add's and 'remove's only.