UI Nits: LTMPlot remove old markers

.. when there is nothing to plot between the
date ranges selected.
fix compiler warning in LTMPlot

.. about unused variable 'middle'.
Merge pull request #451 from jjofre/master

Added Tool to fix heart rate spikes and dropouts
In guiUpdate(), fixed an issue with updating now to current time so that it is updated about every 1 second.
Merge remote-tracking branch 'upstream/master'