add limit what to consider as fragmented

[Kamil Páral]

Please add a new option to specify what is considered as a fragmented file and what is not. For example

-t --treshold x Number of P/MB from which to consider file as fragmented

e.g. $ fidefrag -d -t 0.75 .
meaning only files with >=0.75 P/MB will be defragmented.

If I want to defragment my movie folder, I am really not interested in defragmenting a lot of 700MB files with 0.05 P/MB, which fidefrag currently considers as fragmented, but I want to defragment the rest. This option will allow me to do that.