Change how 1D graphs of Mantid data are plotted

[Nick Draper]

From the Scientific steering committee.

The form of plotting we choose should depend on the underlying data in the workspace.

If the data is histogram data (nX=nY+1) Default: we should plot the values at bin start up until bin end connecting together with horizontal lines. (ideally this option in MantidPlot should be renamed from Horizontal Lines to "Histogram"). Optionally: If the users opts to connect the lines together as points then we should plot the bin value in the center of the bin (as we do now).

If the data is point data (nX=nY) we should plot at X value and connect with lines. (anyoptions for connecting with steps or Histogram should be greyed out)

[Roman Tolchenov]

(In [2207]) 1D plots draw histograms by default. Removed repeated code. re #459

[Roman Tolchenov]

(In [2208]) A bug fix. re #459

[Martyn Gigg]

(In [2209]) A fix for the qtiplot build under Linux. A endif directive had been misplaced so that the linker could only find function definitions on Windows. Re #459

[Roman Tolchenov]

(In [2211]) Corrected workspace creation. re #459

[Stuart Campbell]

This ticket has been transferred to github issue ​1307