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/Zipper.cpp

@@ -1,5 +1,6 @@
 #include <exception>
 
+#include "Exception.hpp"
 #include "Zipper.hpp"
 #include "miniz_extension.hpp"
 #include <boost/log/trivial.hpp>
@@ -29,7 +30,7 @@ public:
 
     SLIC3R_NORETURN void blow_up() const
     {
-        throw std::runtime_error(formatted_errorstr());
+        throw Slic3r::RuntimeError(formatted_errorstr());
     }
 
     bool is_alive()