Eureka (solved): ExpressionChangedAfterItHasBeenCheckedError (setTimeout) #88; sys-check adapted to app-root-approach

HttpclientModule removed from all submodules to enable http interceptor; superadmin status change UI added

iqb-berlin/testcenter-iqb-ng#89
iqb-berlin/testcenter-iqb-ng#82
iqb-berlin/testcenter-iqb-ng#84

first successful run after merging tc + admin; workspace monitor extracted from admin; testcontroller works; syscheck does not work; admin login failed

# Conflicts: (some are resolved directly, most are split into TC and ADMIN version)
#	.gitignore
#	README.md
#	angular.json
#	e2e/src/app.e2e-spec.ts
#	package-lock.json
#	package.json
#	src/app/about/about.component.html
#	src/app/about/about.component.ts
#	src/app/app-routing.module.ts
#	src/app/app.component.scss
#	src/app/app.component.spec.ts
#	src/app/app.component.ts
#	src/app/app.interceptor.ts
#	src/app/app.interfaces.ts
#	src/app/app.module.ts
#	src/app/backend.service.ts
#	src/app/maindata.service.spec.ts
#	src/app/maindata.service.ts
#	src/app/start/start.component.css
#	src/app/start/start.component.html
#	src/app/start/start.component.spec.ts
#	src/app/start/start.component.ts
#	src/app/superadmin/superadmin-routing.module.ts
#	src/app/superadmin/superadmin.component.css
#	src/app/superadmin/superadmin.component.html
#	src/app/superadmin/superadmin.component.ts
#	src/app/superadmin/superadmin.module.ts
#	src/environments/environment.build.ts
#	src/environments/environment.prod.ts
#	src/environments/environment.ts
#	src/index.html
#	src/polyfills.ts
#	src/styles.css
#	src/tsconfig.app.json
#	src/tsconfig.spec.json
#	src/tslint.json
#	tsconfig.json
#	tslint.json

implement endpoint `[GET] /system/config` replacing `[GET] /sysconfig` and preparation for https://github.com/iqb-berlin/testcenter-iqb-ng/issues/53