WIP - added project data model files for well log plots

Added command feature for adding new well log plots (right-click "Plots"
in the project tree view). Will create dummy Qwt widget added as an MDI
window.
TODO: Complete the relations between the entities, and add
properties/property editors. Create more advanced viewer widget for
plotting of multiple traces with multiple curves. Harmonize MDI stuff
with 3D viewers.

ApplicationCode/ProjectDataModel/RimProject.h

@@ -36,6 +36,7 @@ class RimIdenticalGridCaseGroup;
 class RimOilField;
 class RimScriptCollection;
 class RimWellPathImport;
+class RimMainPlotCollection;
 
 namespace caf
 {
@@ -104,4 +105,5 @@ private:
     caf::PdmChildArrayField<RimEclipseCase*>                     casesObsolete; // obsolete
     caf::PdmChildArrayField<RimIdenticalGridCaseGroup*>   caseGroupsObsolete; // obsolete
 
+    caf::PdmChildField<RimMainPlotCollection*> mainPlotCollection;
 };