Dynamic extrusion width for better gap filling
Merge branch 'master' into dynamic-flow

Conflicts:
	lib/Slic3r/ExPolygon.pm
Merge branch 'master' into dynamic-flow
Merge branch 'master' into dynamic-flow

Conflicts:
	lib/Slic3r/Flow.pm
	lib/Slic3r/Layer.pm
Merge branch 'master' into dynamic-flow
External perimeter first on bottom layer when brim is enabled. #761
New faster algorithm for filling gaps, while we work on a new medial axis implementation
Merge branch 'dynamic-flow'
Avoid overlapping regions (thanks Mike Sheldrake!). #726
Distribute skirt loops across all extruders
Remove unnecessary retractions
Remember last used filament presets when using multiple extruders too
Use XML::SAX::ExpatXS if available
Show object information when double-clicking it in the plater
Don't apply slowdown factor to bridges. #640
Bugfix: bed temperature wasn't being set after the first layer when first layer bed temperature was set to zero. #760
Refactored the options group building to allow for more flexible layouts
Independently set number of top/bottom solid layers. #676
Reorder some options using the more compact layout
Update --help with the new --top-solid-layers and --bottom-solid-layers