Added type progress-designator in src/types.lisp

* src/types.lisp (progress-designator): new type; nil, t or a real
  between 0 and 1
  (progress->real): new function; convert a `progress-designator' to a
  real number
* src/conditions.lisp (progress-condition::progress): changed and
  fixed type to `progress-designator'
  (progress): declared type of progress parameter
  (print-progress-percentage): likewise
* src/package.lisp (package more-conditions): added exported symbols
  progress-designator and progress->real
* more-conditions.asd (+version-revision+): bumped revision 0 -> 1