Changes to fixed XES scans not showing time remaining

Added:
REIXSXESScanConfiguration::computeTotalTime(),
computeTotalTimeImplementation() and totalTime()

to compute the time remaining from timer or counts, whichever comes
first and expose the results.
Removed debug
removed errant debugging comment.

I wanted to see if ```emit totalTimeChanged``` does anything...  It
doesn't seem to.  Neither does ```emit progress```...

Hmmm...
Merge pull request #738 from acquaman/Issue636

Issue636