Common:
- renamed report_coverage.sh script to report_coverage_all.sh

Common/DatabaseAPI:
- improved root class validations and test units
- added _RootEntity interface
- improved definition of Context database API entities

Context service:
- added AddLink/DeleteLink rpc methods
- temporarily disabled integration tests

Device service:
- applied renamings in service and test units

General changes:
- implemented data type checker class
- improved database Entity/Collection/Attributes API
- implemented grpc message parsing assertions
- integrated code coverage analyzer and reporter with code testers
- added example topology NSFNET

Common to device & context services:
- improved database context API and its tests

Context service:
- updated context proto file: added AddLink/DeleteLink RPCs, added LinkId to Link
- minor changes

Device service:
- implemented device service functionality
- improved device client
- updated genproto script
- updated device proto file: configure request becomes a Device message
- updated context proto file: operational status: added KEEP_STATUS, changed DISABLED
- moved device tests to global scripts
- extended unitary tests
- temporarily disabled integration tests