mallet_word_plot: more than one word
approaching working with the sampling state

unfortunately the HUGE table again poses memory problems for R. Sigh.
working (I think) read_simplified_state and tytm

Uses bigmemory. So...
working topic-word plot...on the test case anyway

needed only to enforce conversion from sparse to regular matrix at the
key moment in mallet_word_plot

also added a head comment for words_topic_yearly_plot
short is too short for my data!