Editor's UI rework

[nicolas-goyon]

Snap and split

Would be nice to have a way to snap different windows to the sides, top and bottom of the screen, splitting the bottom into two half to have two windows (like the hierarchy and the console)

Hierarchies and lists

Being able to smaller lists with smaller icons (or removed ones) maybe using SVG icons could help that process. The idea would be to display more elements without scrolling. the size of each line could be editable for those who still want to keep bigger icons.

Files management

Being able to create, open, delete files from the editor. Creating files will also help creating multiple kind of files by adding the basics of each files, saying we want a new scene, we could be able to have a button to create everything to the new scene. Same for lua and cpp scripts. The idea would be to have a way to create classes and other kind of scripts with the basic information and comment inside. By douple clicking on it, we would be able to open it with either the default Windows' editor or for an editor specified in the settings by adding the path or anything like this. The idea would be to use the editor instead of the file manager.