STRAMBIO -- Add Objective CoverglassThickness field

[strambc]

Proposed change

Element name(s): Objective

Justification for the addition:
Objectives often specify the thickness of the coverglass they are designated to work with.
This is currently not recorded.

Full description of the proposed addition (enough detail to implement):

• New Field name(s): CoverglassThickness
• New Field data type: xsd:string
• New Field requirement level: Optional
• New Field Tier level: 2
• New Field description: "This field records the range of Coverglass Thickness this Objective is designed to work for, expressed in mm."

[JSDLacoste]

Just to clarify, if we accept this change, the model will contain two very similar fields there will Objective/CoverGlassThickness AND Sample/CoverGlass/Thickness. The two can be different. Creating possible confusion. This should be addressed before making changes to the model, so that there is no confusion and/or conflict.
For example instead, call it Objective/NominalCoverGlassThickness.