add some commands to HP8904 device

many improvements:

Add an option to qgpib_plotter to make it auto display any newly received plot (+ fix in plot list management)

fix small bugs in qgpib plotter

add ability to print a plot in qgpibplotter

force display of opened file, instead of just adding ot to the plots list

started developer doc

small cleanups and doc update

Improve docs.

Moved .plt example files in a hpgl_plots subdirectory.

(0) -10 +10 tip

mercurial