Include hand / leg / arm part selected in the relation module tooltip in the summary window

[kvesik]

There will still be other elements to add to the Relation Module abbreviations (broader issue is #197), but let's add at least the bodypart info (when applicable/available) for now, to RelationModule.getabbreviation().

Originally posted by @kvesik in #197 (comment)

[kvesik]

Example of intended behaviour:

1. Create a new Relation module and select (eg) Arm1 and Leg2 as X and Y.
2. Click the "Specify arm parts" button to select an arm part (let's say "Arm (contralateral)"), then close the arm part dialog.
3. Click the "Specify leg parts" button to select a leg part (let's say "Legs and feet>knee"), then close the leg part dialog.
4. Select a timing point or interval for the Relation module, then Save and close.
5. The sign summary window shows the newly added Relation module. When the user hovers the mouse over the module the tooltip should show a substring (just what's related to arm/leg/handpart, for now) of the abbreviations shown in the "List of Abbreviations" spreadsheet (link to specific range).

Ask Kaili or Grace if you have questions about the body parts, surfaces, or sub-areas.