doc: Update refcard.tex content from Octave 3 to Octave 8 refcard.tex: Remove Readline material, expand Octave examples. The intended audience of this reference card is someone who already knows programming in a different language like Python and is referring to this refcard.ps / refcard.pdf for Octave syntax. It is not a comprehensive reference, but gives enough function names to be useful with help / doc. Intended length 2 pages.

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