Fix indent in plot function
Change variable names, add output (fighandles)
Create new publicly accessible property 'handles' which saves plot information
This should be some structure, saving all handles for figures, axes, objects
Remove output of plot function - won't be needed anymore
New calling structure for plot: use list of what to plot in varargin, check for existing handles before deciding what to plot
Change handles to a function - this will be used to get the correct handles, and to set the correct handles
This matters when O is multidimensional!
Add possibility to get list of plots which are available from plot function
Move checks on close and available plots to beginning
Move handles_structure to public (temporary)
Extend check on presence of results to consider all entries in in the input vector
Separate handles structure into separate vectors for simplicity
Rename input, make closing compatible with multiple inputs
Implement all plots
Missing:
* Styles, legends (especially for C-T diagram)
Improve plot function: style for series (also effective series) and for the operating diagram now better
Update plot help and output of list of available plots function

Fixes 81
Make the handles properties read-only and transient (they are not saved)
some bugfixes
Merge remote-tracking branch 'origin/CleanupPlot'