WIP: Customer edit/create forms

Context: https://git.happy-dev.fr/startinblox/applications/sib-app/issues/346

Hi @gaelleM ! I've made the following changes in this branch customer-edit:

• Left menu for projects working on user nested now (like with circles)
• Create and edit customer forms (the create form is duplicated as a workaround https://git.happy-dev.fr/startinblox/framework/sib-core/issues/587)
• Edit project changed, + and edit icons needed for opening the above forms
• Create project changed, + icon needed

Could I have some CSS on this please? :)