Add modify feature interaction and its example
Make modify interaction use FeaturesOverlay

Instead of a whole map.
Bring MultiPolygons back in examples
Move variables declaration at the top
Force remove vertexFeature when there’s no features left in FeaturesOverlay
Ensure styles are defined in FeaturesOverlay
Add style for Geomettry Collection
Move segment writers in their own methods
Add support for GeometryCollection in modify interaction
Use Select interaction in modify interaction example.
Store mouse last position to draw vertex at feature selection
Make interaction ctor only have an option object
Render style for Point inside GeometryCollection.
Remove useless style method
%s/render.FeaturesOverlay/FeatureOverlay/
Use strings for GeometryType in examples
Use closure for styles & fix case
Check segment writers existence
Merge pull request #1654 from tonio/vector-api-modify

Add Modify Interaction