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

- Implemented temporary hack to reduce memory used

Update 1-1-1-create-vm-oracle-virtualbox.md to clarify Ubuntu Server should be use instead of Desktop

refactor(policy): add validation at PolicyRuleDevice

See merge request teraflow-h2020/controller!161

refactor(policy): add validation at PolicyRuleService

See merge request teraflow-h2020/controller!160

refactor(policy): add validation at PolicyRuleCondition

See merge request teraflow-h2020/controller!159

- 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