- made frontend a module

- Arranged GitLab CI/CD
- Relocated test files

- Added curl as dependency for unitary tests
- Added configuration settings in Frontend
- Removed unneeded logs

- Arranged GitLab CI/CD
- Added log messages

- Arranged GitLab CI/CD and Docker build
- Configured code coverage
- Grouped test scripts
- Instrumented source code and Makefile for code coverage reporting

- Arranged ports in GitLab CI/CD unitary tests
- Added env-var dump for tests

- activated GitLab CI/CD to adjust the component

Unitary test:
- Corrected Objects definition
- Added devices and links to topology

Frontend component:
- Implemented parsing of backend reply and composition of front-end reply
- Other minor arrangements

Merge branch 'develop' of https://gitlab.com/teraflow-h2020/controller into feat/pathcomp-component-frontend

Merge branch 'develop' of https://gitlab.com/teraflow-h2020/controller into feat/pathcomp-component-frontend

Merge branch 'feat/pathcomp-component-frontend' of https://gitlab.com/teraflow-h2020/controller into feat/pathcomp-component

- fixed parsing of custom rules in unitary tests

- Added missing log dump in unitary test

Common and Context changes:

See merge request teraflow-h2020/controller!157

- added exposition of redis-tests service for testing with Redis backend
- moved delete logic from Context Servicer to ORM components
- added support for constraints of different kinds