Improvements to plotting: displaying distributions and errorbars

[mantid-builder]

Original Reporter: Steve Williams

Allow plots to show raw count data as distributions, add defaults for this displaying errorbars.

• Add units to the matrix view tabs
  • decide what to do with large unit names and implement
  • test
• create plot as distribution functionality
  • convert existing plots to distribution view
  • update the scale and axis legends
  • all future drawing to the plot to be distribution
  • create an is_equally spaced bin? helper function
  • create and test rules for displaying as distribution
• add menu items
  • right click menu items on plots
  • preferences in the view->preferences
• when adding data to an existing plot, make it have the same defaults
  • inherit the errorbar display setting
  • inherit distribution/non-distribution view
• document distribution view
  • MantidPlot:_Help
  • Python help

[mantid-builder]

This issue was originally trac ticket 1238