Instead of expecting callers to know how the size of directory file infos
relates to which files are in which directories, filesystems now offer a
GetRoot() method, and file infos offer a way to get their children. As
a bonus, m_FileInfoVector no longer has to be created and kept around
in RAM. Only the file info objects that actually are used are created.
Makes the information panel self-contained.
This was done first, as opposed to isolating the GameConfig panel--the
first panel in the group--as this panel had code all over the place in
ISOProperties, so I figured it'd be best to fix this one up first.