nPlot 0.4.8 released

Yesterday, GNU/Linux packages of the version 0.4.8 were released; Windows package will be available as soon as some issues with the build are resolved.
Changes:
* Fixed a bug with deleting chart elements which potentialy could lead to a segmentation fault
* Added ability to save and load session files
* Chart is now drawn with Cairo for consistency with exports
* Added ability to plot data in different colors
* Chart can be now scrolled with right mouse button
* Added legend
* Lots of other improvements