plotting tools
- new option --theory-rel-errors to plot relative theory errors in data plots, for theory only plots
- save chi2scan canvas in the root file, and save as separate plot with the splitplots options



git-svn-id: https://svnsrv.desy.de/basic/h1fitter/trunk@1521 b2a8d302-ca0a-427a-b7b9-081adbce06bc
implmented comments from Graeme

git-svn-id: https://svnsrv.desy.de/basic/h1fitter/trunk@1522 b2a8d302-ca0a-427a-b7b9-081adbce06bc