Add 'title' option to display a title on the left or right axes.
This is primarily designed for the graph2d line graph.
Tidy up example
Add 'style' option to group for lineChart.
Allows overriding of class definitions which provides a much simpler interface for programatically setting user defined options.
Add documentation.
Add documentation for axis titles.
Add style option for axis titles.
Update icon to reflect style
Add decimal option for formatting axis labels
Catch case where title is undefined
Update demo
Merge branch 'graph2d_decimals' into development

* graph2d_decimals:
  Add decimal option for formatting axis labels
Merge branch 'graph2d_add_title' into development

* graph2d_add_title:
  Update demo
  Catch case where title is undefined
  Add style option for axis titles.
  Add documentation for axis titles.
  Tidy up example
  Add 'title' option to display a title on the left or right axes. This is primarily designed for the graph2d line graph.

Conflicts:
	lib/timeline/component/DataAxis.js
Update examples
Update documentation
Add style option for data points.
Note that this ought to be renamed to be consistent with other style options but currently 'style' is used to define the shape of the point.
Add fill styling option
Update demo.
Update documentation
Merge branch 'graph2d_styling' of https://github.com/cdjackson/vis into cdjackson-graph2d_styling
Merge branch 'cdjackson-graph2d_styling' into develop

Conflicts:
	lib/timeline/component/DataAxis.js
	lib/timeline/component/LineGraph.js