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.
Refactored Arrange interface: remove the union based BedShapeHint, replace it with proper function overloads
WARN: this commit is only intermediate, it does not compile.
Reworked the FFF testing framework & ConfigBase::set_deserialize()
for more compact tests: set_deserialize() now accepts list
of key / value pairs.
Fixed an incorrect assert in LayerRegion.
DynamicPrintConfig::full_print_config()
new cheaper constructors of DynamicConfig / DynamicPrintConfig from ConfigBase
Unit tests: ported test_model from upstream Slic3r, thanks @lordofhyphens
Unit tests refactored to use less autos and initializer lists for readibility,
DynamicPrintConfig is handled by value, not by shared pointer.
