ENH: Implement queries and entity retrieval

.docker/caosdb_client.json

.docker/install_cpplib.sh

.gitlab-ci.yml

CHANGELOG.md

Project.toml

README_SETUP.md

docs/src/api.md

docs/src/examples.md

src/Authentication.jl

src/CaosDB.jl

src/Connection.jl

src/Entity.jl

src/Exceptions.jl

src/Info.jl

src/Transaction.jl

src/Utility.jl

test/runtests.jl