Update of terminologies

[lzehl]

The terminologies, or specifically the terminology definitions should be updated and made a bit more generic.
Example, the definition of Subject currently states:
"The investigated experimental subject (animal or person). May contain the Cell and Preparation sections as subsections."
The first part is awesome, the second sentence is unnecessary and too specific.
Subject section could also contain a Training or a Surgery subsection.

Updating the terminologies should depend on the outcome/solution of #138. If the G-Node OEN can be linked and the definition with this automatically set we only have to correct/maintain one source instead of two.