DesktopFile.Class enhanced to handle complex desktop files

Merged username-removed-1551145 requested to merge amorehen/gambas:master into master

[gb.desktop]

  • NEW Actions property -- returns a string array of the names of additional [Desktop Actions ...] sections
  • NEW AlternativeActions property -- returns a collection of action names (key) and action exec commands (value).
  • NEW WorkingDirectory property -- returns the application's working directory
  • NEW RunAsRoot function -- runs the application as root
  • NEW Language support added to additional properties