* added wrapper to SliderFloat in imgui
* fixed localized text in Mouse3DController
* added take_snapshot for extruder change in object list
* fixed text typos in AppConfig.cpp, ConfigWizard.cpp and ConfigManipulation.cpp
The gap fill was disabled for zero infill.
Now the gap fill is enabled in between the perimeters, but disabled between
the inner-most perimeter and infill in case the infill is set to zero.
Also in case there are multiple infill regions inside a perimeter,
the mutliple infills are considered as non-zero if at least one infill
is non-zero, therefore the gap fill will be added inside the inner-most
perimeter.
