MVPlot. Easy and flexible TAG based plot

% function mvplot(varargin)
% =========================
%
% Flexible plot function which exploits VARARGIN in order to define the
% components of the chart and their characteristics.
%
% The function is based on a sequence of <'feature',value> couples
% The 'feature' is a tag (string) for selecting a particular characteristic of the
% chart; the value sets the selected characteristic. The data type of the
% value depends on the handled characteristic.
%
% EXAMPLE
%
% x=1:10; y=2*x+3
% mvplot('x',x,'y',y,'title','My sample title','legend','MyData');
%
% LIST OF TAGS
% ============
%
% x : x values (numeric)
% y : y values (numeric, MANDATORY)
% xlabel, ylabel : axes labels (string)
% title : figure title (string)
% titlefontsize : title font size (numeric)
% linestyle : style of the line (Matlab format)
% linewidth : width of the line (numeric)
% legend : legend entry for the current data serie (string)
% legendfontsize : legend size (numeric) [the last update of this feature within the
% same figure determines the fontsize of the whole legend]
% fillspace : if specified reduces the margins of the figure