Add resolution-related terms and definitions

[Zack-83]

Closed #125

[StroemPhi]

Again many thanks!

[StroemPhi]

@Zack-83 I've linked to the terms in the CHARISMA wiki that you provided in the issue, apart from the Pixel resolution , since we didn't define it here. Should we, or can we ignore it?
If we should also define it, then I propose opening a new PR for it, so we can merge this one.

[Zack-83]

@Zack-83 I've linked to the terms in the CHARISMA wiki that you provided in the issue, apart from the Pixel resolution , since we didn't define it here. Should we, or can we ignore it? If we should also define it, then I propose opening a new PR for it, so we can merge this one.

Clearly the definition of "image resolution" (~ NUMBER of distinct neighbouring measurements) is not coherent with the definitions of "optical resolution" (~ DISTANCE between neighbouring measurement values) considered in the present PR. Therefore I agree with you to leave this term out.