Add admin module

client/src/app/admin/admin-routing.module.ts

client/src/app/admin/admin.module.ts

client/src/app/admin/components/admin-nav.component.html

client/src/app/admin/components/admin-nav.component.scss

client/src/app/admin/components/admin-nav.component.ts

client/src/app/admin/components/index.ts

client/src/app/admin/components/instance-card.component.html

client/src/app/admin/components/instance-card.component.scss

client/src/app/admin/components/instance-card.component.ts

client/src/app/admin/containers/admin.component.html

client/src/app/admin/containers/admin.component.ts

client/src/app/admin/containers/instance-list.component.html

client/src/app/admin/containers/instance-list.component.scss

client/src/app/admin/containers/instance-list.component.ts

client/src/app/app.module.ts

client/src/app/metamodel/store/models/instance.model.ts

client/src/app/shared/shared.module.ts

client/src/styles.scss