Improve copy/move performance with nio and reintroduce cancel.

Utilize FileChannel.transferFrom to copy files faster. Chunk the file
transfer so that we can check between each chunk if the user has
cancelled the copy.

In my tests copying a large file (650MB), this improved performance by 45%.

Also, bring the cancel feature back for non secure storage.

Fixes QRDL-976.

Change-Id: I112cee7b9dfe682a438516f7f938dfd7538f1efb