rework selection

[jimy-byerley]

Currently, clicking selects the an element of a view item, and this item and every object containing this item are considered selected. Tools using the selected objects need to filter them in order to keep the objects of th eright type (and taking care to not pick its parents or children as well)

There is downsides to this

• only the subitem is shown selected, nothing is witnessing that all parents objects are selected as well
• we cannot express we want to work with a subpart rather that an upper level (for instance we cannot select a Solid but not its content, nor select a mesh but not one of its groups ...)

A better way (that needs some changes in the rendering pipeline) would be to have only the subitem selected on the first click, then additional clicks (or an other shortcut ?) is switching the selection to the upper level. Selected objects will be rendered with a selection outline like in blender.

[jimy-byerley]

Also better to switch to exclusive selection (clicking and object selects other object unless shift is pressed) like blender did. It should be more intuitive