The original filesizeformat was broken: the largest prefix was for base ** 3 (GB/GiB) and the prefix for "kilo" was wrong (the 1000 prefix should be "kB" with a lowercase "k", only the binary prefix has a capital "K"). This should also future-proof it until we have to worry about what's larger than a yottabyte (the SI hasn't decided yet, it seems).
base ** 3
Fixed filesizeformat filter. It should now conform to the official SI…
… prefixes and use the correct prefixes for sizes greater than base ** 4.