Review left column menus display

Today issues:

• Project and Settings & Versioning sections do not show indications that they are actually menus. This is confusing for users who do not understand they can open the Settings & Versioning menu for instance.
• Browsing in one section close the other one and it's painful to reopen it each time you need it.
• The sections are not really readable because of all the graphical elements

Things to do in the ticket:

• Display the menus as simple divs that you can scroll
• Remove categories icons
• Update + and - icons on tree (old and pixelated)

Things to do in addition:

• Rename sections from "Project / Settings & Versioning" to "Design & Code / Source Control / Definition & Dependencies" -> see NXS-1897
• Remove actionbar (new, import, download, commit) -> see NXS-1865
• Review info box -> see NXS-1905

The ordering of categories (resources, branding, content model, etc ..) in each section is not the purpose of this ticket and should be done separately when needed.