When selecting multiple files in a changelist P4V's 'Change Filetype' dialog should support tri-state checkboxes.
When opening the dialog the checkboxes should be:
* checked if every file has the corresponding type
* unchecked if none of the files have the corresponding type
* indeterminate (tri-state) if only some of the files have the corresponding type.
Hitting OK without modifying an indeterminate Filetype should leave that type unchanged on every selected file.
This change would allow individual Filetype bits to be set or unset without changing every selected file to have the exact same Filetype. For example adding or removing the +l Filetype on a mixed selection of text and binary files with various storage flags.
Right now if you select multiple files it will change every selected file to match the state of the dialog when hitting the OK button. It should only modify the bits that were changed on the dialog. This is usual undesirable.