* Refactor interface to PdmObjectHandle and PdmFieldHandle
Return objects instead of passing in structures as parameters
* Add nodiscard to several functions
* Remove redundant this->
* Rename to ptrReferencedObjectsByType
* Add shortcut for Plot Editor, and modify how command features are triggered
Use Ctrl-E to launch the Plot Editor.
* Add optional use of NOECHO and ECHO keywords in GRDECL files
* Add ECHO keywords to sector model export
* Add Help button to Preferences