setcomprehension_pointfree simproc also works for set comprehension without an equation

tuned message -- avoid extra blank lines;

updated to polyml-5.5.0 which reduces chance of HOL-IMP failure (although it is hard to reproduce anyway);

store colors after build

adding further test cases for the set_comprehension_pointfree simproc

refined tactic in set_comprehension_pointfree simproc

adding further test cases to check new functionality of the simproc; strengthened test cases to check the success of the simproc more faithfully

adding postprocessing of computed pointfree expression in set_comprehension_pointfree simproc

extending the setcomprehension_pointfree simproc to handle nesting disjunctions, conjunctions and negations (with contributions from Rafal Kolanski, NICTA); tuned

more informative error of initial/terminal proof steps;