Translate the Concept API classes

[mkschulze]

It's about these files: https://github.com/Humans-of-Julia/GraknClient.jl/tree/dev/client-python-reference/grakn/service/Session/Concept

[mkschulze]

maybe we can use this to make translation easier: https://github.com/ipod825/OOPMacro.jl

[mkschulze]

Better to wait for finished client-python 2.0, so we see how to start ideally.