STA pre-validation issues

Manage external tools

• No user help provided (help does not appear)
• No developper help provided (wiki page on confluence)
• source product, source product file and target product file parameters can't be edited or suppressed
• Modify to tool: when no tool is selected, to dialog disapear and nothing is launched, this dialog should not disapear until "close" is pressed.
  
• After integration of an "Notepad++" processor, the processor doesn't start, the following traces appear: com.bc.ceres.binding.ValidationException: Value for 'target product directory' must be given   at com.bc.ceres.binding.validators.NotNullValidator.validateValue(NotNullValidator.java:29) ... at org.esa.snap.ui.tooladapter.ToolExecutionForm.<init>(ToolExecutionForm.java:56)