there is a problem - submenu item gets checked when parent menu item is checked.
fix for the problem - when you restart the application the last selected submenu item gets checked.
remove unnecessary using
applied changes to TaskSettingsForm. reused code from MainForm.
removed unnecessary code that remained after making ImageFileDestination, TextFileDestination not nullable.
Added comments
fix comment
Merge pull request #284 from barsv/fix_1_menuChecks

Code improvements and fixes for pull request "Change check behavior for Destinations->Image uploader->File uploader #283"