behaviour of tptp_graph now depends on an envir variable to indicate whether to produce proof graph containing formulas or not; tuned;

experimented with presentation of DOT+LaTeX;

edges are now being shown in the proof graph; removed the shapes related to the conjecture and the negated conjecture, to remove clutter (since i'm also showing the inference's conclusion in latex);

added case for handling 'assumption' lines in Satallax proofs;

improved latex output: spacing between terms, and encoding terms in mathrm; tuned comments;

experimenting with improving DOT output, and embedding LaTeX code for formulas (rather than only giving the clause number);