WIP plugins: list installed plugins in client

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

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

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

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

client/src/app/+admin/plugins/index.ts

...lugin-list-installed/plugin-list-installed.component.html

...lugin-list-installed/plugin-list-installed.component.scss

.../plugin-list-installed/plugin-list-installed.component.ts

...+admin/plugins/plugin-search/plugin-search.component.html

...+admin/plugins/plugin-search/plugin-search.component.scss

...p/+admin/plugins/plugin-search/plugin-search.component.ts

...lugin-show-installed/plugin-show-installed.component.html

...lugin-show-installed/plugin-show-installed.component.scss

.../plugin-show-installed/plugin-show-installed.component.ts

client/src/app/+admin/plugins/plugins.component.html

client/src/app/+admin/plugins/plugins.component.scss

client/src/app/+admin/plugins/plugins.component.ts

client/src/app/+admin/plugins/plugins.routes.ts

client/src/app/+admin/plugins/shared/plugin-api.service.ts

client/src/app/core/plugins/plugin.service.ts