Consistency on arrows

[Bouh]

All changed are made accoring to the design, expect for some because I don't know how to manage them:

• The behavior in the object dialog, that use Accordion from Material-UI that auto flip the icon.
• The select list, that use Material-UI too, I can see the select and the option inside but I can't find where is the icon.

// TODO

• The eventsheet are using images, I need to replace them and handle padding/background colours. I used SVG as recommended.

[AlexandreSi]

Using ChevronArrowXXX in TreeView required to increase the size of the SVG so that it's not too small, which is a good thing because the clicking area is increased, but a bad thing because it messed up the alignment of icons.
I think those icons in the TreeView (and ReadOnlyTreeView now also) should be handled directly with SVG outside of material-ui.