* Renamed TimelineSizer.* to TimelineWindow.*
+ TimelineWindow is now hidden by default
* onAdd and onDelete tape now use references

For TapeUser. Changed onAddTape and onDeleteTape to use references to
Tape, instead of pointer to tape, to help convey the fact that they'd
never be NULL, in contrast to onSelectTape, which may.
* Cleaned up the header files

Added the header guards I forgot because I wasn't thinking, normalized
spacing, normalized style a bit, etc.