At last - accurate tape accounting?

So it seems we now have accurate tape accounting - CMS have looked at the new numbers generated by the new CIP code and declared that it matches their expectations.

The code accounts for data compression as it goes to tape - and estimates the free space on a tape by assuming that other data going to the same tape will compress in the same ratio. Also, as requested by ATLAS, there is accounting also for the "unreachable" data, ie data which can't be read because the tape is currently disabled, or free space which can't be used because the tape is read-only.

All the difficult stuff should now be complete: the restructuring of the internal objects to make the code more maintainable, and the nearline (aka tape) accounting. Online accounting will stay as it is for now.