refactor: Decouple services that needed for monitoring (alarms) and based common policy services. Didn't change any of th existing implementation.

refactor: change the Add , Delete , Update ztp services . Add exception handling for external services and remove unnecessary device==null exception handling. Create an internal exception handling mechanism for all the uni failures.

# Conflicts:
#	src/policy/src/main/java/org/etsi/tfs/policy/policy/PolicyServiceImpl.java
#	src/policy/target/kubernetes/kubernetes.yml

Resolve "(UBI) Error handling in ZTP component"

See merge request !228

- Updated README.md file
- Fixed libyang version in Dockerfile
- Fixed libyang version in install_requirements.sh
- Added folder libyang to global gitignore
- Added generation of .gitignore file for libyang/build

Resolve "Fix libyang version in NBI component"

See merge request !230

Merge branch 'develop' of ssh://gifrerenom_labs.etsi.org/tfs/controller into feat/148-ubi-refactor-policy-component

Feat/148 ubi refactor policy component

See merge request !229