Adding gallery* examples, and introducing plotting behavior

gallery:
   + random, vandercheb, vandermonde
   + relevant tests

gallerytrig:
   + noisyfun, random, sinefun1, sinefun2, starburst
   + relevant tests

Also, per Toby’s suggestion, if no output argument is supplied the gallery functions create a plot of the selected function (whether or not it is random). The plot has suitable axis limits, and the title of the plot states the name and length (or rank) of the function.