(1) add eclipse project support;
(2) implement opacity style validation;
(3) refactor ttml10 style validator to support different accessor value types, e.g., String vs Float;
(4) add opacity valid (with warning) tests;
(5) change treatment of negative extent lengths to error (rather than warning);
(6) add extent invalidity tests;
(7) rename --list-models to --show-models;
(8) add --hide-warnings option;
(9) show processing options state prior to validation if using verbose mode, e.g., show if warnings are disabled, hidden, etc.;
(10) update MD documentation;