Introduce a bare-bones postgres DB scheduler (#1229)

.gitlab-ci.yml

CMakeLists.txt

ReleaseNotes.md

...ousintegration/docker/ctafrontend/cc7/opt/run/bin/init.sh

continuousintegration/orchestration/create_instance.sh

cta-release/CMakeLists.txt

cta.spec.in

disk/CMakeLists.txt

frontend-grpc/CMakeLists.txt

frontend-grpc/Main.cpp

scheduler/ArchiveMount.cpp

scheduler/CMakeLists.txt

scheduler/GenericSchedulerTest.cpp

scheduler/OStoreDB/OStoreDB.hpp

scheduler/OStoreDB/OStoreDBFactory.hpp

scheduler/PostgresSchedDB/ArchiveJob.cpp

scheduler/PostgresSchedDB/ArchiveJob.hpp

scheduler/PostgresSchedDB/ArchiveJobQueueItor.cpp

scheduler/PostgresSchedDB/ArchiveJobQueueItor.hpp

scheduler/PostgresSchedDB/ArchiveMount.cpp