Added ability to resize the plot to a given size.
 Patch for Issue 707 and 778 

- Fixes the issue where steps altering user datapoints
- Do not altering user data points for drawing lines with steps 
(even stacked); just consider drawing with steps enables a different 
kind of plotting and clipping on lines and areas; that assuming that 
drawing with steps must always go horizontally and then verticaly 
(like previous inserted datapoints).
Put a tab instead of with spaces
Merge pull request #1188 from mcamenzind/0.9-work

Added ability to resize the plot to a given size.
Merge pull request #1194 from jBouyoud/0.9-patch-707-778

 Patch for Issue #707 and #778 (0.9-work)
Merge remote-tracking branch 'upstream/0.9-work' into FixIssues