Bug fix #265.
Added expression checks for default values and updated the model according to those checks
Allowed to have two model elements for expressions and statements
  - One for interpretation
  - One for logging errors
Handle the cache correctly
Version number
Disable CANCEL button for some actions
Display sorted requirements
Allow copy & paste
Bug fix
Display comments in green, prefixed by //
Bug fix : ensure that the target direectory exists before saving the file
Bug fix
Corrected DMI Available state
Reviewed positions of states in state machines
Corrected tests (deadlines of expectations) after changes on DMI
Corrected DMI available state for inputs
Bug fix: reqrefs to unexisting paragraphs launched an exception
Merge branch 'openETCS/master'