make units more dynamic and automatically switch between [kMGT]iB

Some examples of before and after, this applies for Swap- and
MemoryMeter:

622/7770MiB
622.7MiB/7.8GiB

0/2048MiB
420kiB/2.0GiB

555/131072MiB
555.8MiB/128.0GiB

442368/1048576MiB
432GiB/1.0TiB