WIP Refactoring of exceptions:

1) All slicer's exceptions are now derived from Slic3r::Exception.
2) New exceptions are defined for slicing errors.
3) Exceptions are propagated to the Plater to show.
It remains to modify the slicing back-end to throw the new SlicingError
exceptions instead of std::runtime_error and to show the other exceptions
by a message dialog instead of a notification.

src/libslic3r/Fill/FillBase.cpp

@@ -2,6 +2,7 @@
 
 #include "../ClipperUtils.hpp"
 #include "../EdgeGrid.hpp"
+#include "../Exception.hpp"
 #include "../Geometry.hpp"
 #include "../Surface.hpp"
 #include "../PrintConfig.hpp"
@@ -40,7 +41,7 @@ Fill* Fill::new_from_type(const InfillPattern type)
     case ipOctagramSpiral:      return new FillOctagramSpiral();
     case ipAdaptiveCubic:       return new FillAdaptive();
     case ipSupportCubic:        return new FillSupportCubic();
-    default: throw std::invalid_argument("unknown type");
+    default: throw Slic3r::InvalidArgument("unknown type");
     }
 }