eliminated somewhat redundant inlined name (despite a7aa17a1f721);

clarified modules;

tuned signature;

clarified module name: facilitate alternative GUI frameworks;

--HG--
rename : src/Pure/GUI/swing_thread.scala => src/Pure/GUI/gui_thread.scala

separate module "GUI", to keep this out of the way of generic Isabelle_System operations, notably for non-Isabelle/jEdit applications;
tuned signature;

avoid -Infinity which confuses JFreeChart histogram;

updated headers;

accomodate scala-2.9.2;

use inlined session name as title for charts;
tuned signature;

charts for future task runtime statistics;