Refactoring PaganinIterator

Preparing for new pipeline and selective slice reconstruction.
Putting the necessary stuff into own functions to make code a bit
clearer.
Loops for iterating through Delta and Beta should be more clear now,
since the "work" stuff is made via functions.
Now I need to implement the "selective reconstruction", which means that
we only want to reconstruct a set of sinograms, so the whole thing goes
quicker.
But for this I need Fedes help.
Refactoring

Make it only work on 'cons-2', otherwise switch to 'test' mode.
Getting rid of all os.path.abspath by calling it once at the beginning.
Trying to debug this thing, I wonder why 'subprocess.check_call' doesn't
seem to work on 'cons-2'.
More error checking in the middle and completely redoing the fiji call
at the end.
PaganinIterator refactored (wating for Fede)

Cleared up help and streamlined output to console.
After finding out that 'subprocess' needs a list (Thanks Heiner!)
switching the 'verbose' logic to the call of subprocess.
Writing the commands to a log file, so they could be redone after
the fact.
Only give the Fiji-call when we're not testing and informing the user
that there's a log file to look at after we're done.
No wildcard imports anymore
Cleanup with logging, tested version.
Logically separate plotting and output

Before the plotting of the curve happened at the beginning and the end
of the file and the output in the middle, now it's more logically
separated.
Merge branch 'paganin-multiprocessor'