First working version of Device with Emulated and OpenConfig drivers (except device monitoring)

See merge request teraflow-h2020/controller!38

Deactivated some Device monitoring functionality partially implemented to enable a functional commit into develop.

Device:
- Implemented Driver API with some special resources to enable retrieving endpoints from devices, interfaces, and network instances.
- Implemented special resource_keys (_connect/*) to enable AddDevice to obtain settings used to connect to remote devices (address, port, username, password, etc.)
- Implemented Emulated Driver (only for testing)
- Implemented OpenConfig Driver (missing to implement monitoring; templates for Infinera devices to be tested with other device vendors)
- Minor bugs and code improvements
- Improved test unit to enable easy testing of vendor devices and keep credentials secret.

Integrated L3 services UPM

See merge request teraflow-h2020/controller!29

# Conflicts resolved:
#   .gitlab-ci.yml

Renaming the monitoring yaml file to follow the pattern expected by the  script.

See merge request teraflow-h2020/controller!37

feat: implementation of Policy service

See merge request teraflow-h2020/controller!36

feat: streams implementation for automation service

See merge request teraflow-h2020/controller!34

- reorganized some files and modules
- implemented discovery of device endpoints for OpenConfig driver
- implemented retrieval of current configuration for OpenConfig driver
- updated test units and separated in emulated and openconfig test sets

- added missing proto files in genproto.sh
- created .gitignore files to prevent sharing device credentials and data
- improved MonitoringLoops class with one thread per driver for data collection, a unique aggregation queue and one single thread for data export to monitoring
- added GetResource method to Driver API
- improved DriverFactory to select the driver that better fits with filter fields in terms of number of correspondences in filter fields. Drivers with some mismatch filter are discarded.
- implemented proper initialization and connection of drivers to real devices
- started to implement OpenConfig driver with support for Infinera Packet Routers

- Implemented Database models for KpiModel and KpiSampleType
- Added MonitorDeviceKpi to DeviceClient
- Added MonitorDeviceKpi to DeviceServiceServicerImpl (partial implementation)
- Created MonitoringLoops class (partial implementation)

Merge branch 'feat/monitoring-service' of https://gitlab.com/teraflow-h2020/controller into feat/device-adapt-to-context-api

- Subscriptions to be implemented