Bugfix: sometimes a tiny gap was left between infill and perimeters. Includes regression test. #1803
Remove weak test. #1803
Better logic for gap fill: don't subtract from fill surfaces those gaps that medial axis was unable to fill. Thanks ledvinap for the idea and proof of concept implementation. Includes a tolerance factor for avoiding being too strict when collapsing loops (allow some overlap if that helps avoiding triggering medial axis). #1803
Regression test for numerical issues causing thin gaps between perimeters and infill. #1803
Fixed regression in --infill-only-where-needed. Includes a minimal test suite for such feature. #1871

Conflicts:

	t/fill.t
Bugfix: ExPolygon::contains_line() was called with a Polyline object but didn't throw any error. Thanks ledvinap #1945
Removed duplicated method added to Slic3r::Line in caf20664cd72919996798643cceb8d04b4191995. #1945
Default extruder wasn't applied to perimeter extruder. Includes regression test. #1868
Always do one island at time instead of doing that only when avoid_crossing_perimeters is enabled. #1907
Clarify that we need single configs instead of bundles
Bugfix: [filament_preset] was not replaced in filename when using Quick Slice. #1870
Bugfix: crash when extending an array option by 2+ positions. #1908
Fixed regression when concentric infill was used as solid infill. Includes regression test. #1650
Bugfix: wxWidgets on Windows needs Skip() on kill focus to prevent nasty focus bugs. #1873
Fixes for the last commit about kill focus. #1873
Handle EVT_TEXT on wxSpinCtrl too
Set min temperature to 0
Workaround wxWidgets not allowing SetValue() inside a EVT_COMBOBOX handler on Windows. #1865
Workaround for upstream module bug causing command line option parsing for multi-boolean options like retract-layer-change and wipe
Test coverage for retract_layer_change