Simplified feedback of gather to gen

It shows that the channel pattern is overkill there, and much to
complex compared to what we really have to achieve.

Prepared usage of stat structure for all statistics, also those used by agg
Using statistics struct for everything now, reducing overall complexity.

Additionally, the progress format looks much cleaner now thanks to padding setup
Added support for copying and hashing symlinks, as well as reproducing the file-mode.

This is already a good start to make it into a general-purpose data duplication tool.
Implenented file filtering.
Improved handling of files which changed size on disk when verifying it.
Reorganized cmd startup and made sure there is one gather proc per device.

However, even though tests run, in the real world I still have only one
reader, apparently.
Something is wrong, and I will find out what exactly ;) !
Each generator and gather pair now has their own file channel.

That way, they won't compete with others.
For some reason, there is still no improvement - multiple read controllers
don't want to work in parallel.
The files come in in perfect alteration ... .
Can it be that gob is synced ??
Once again, I was hit by not properly copying values.

It's all clear now, will hopefully not happen again.

With go-routines in a loop, copy values that change in there. Value-types
must be copied as well, of course.
Now it's impossible to have duplicates in the input list.

Previously, and after the path-separator-fix, this was possible once again.