For 36807, fixes for shot name editing

[sgsteph]

• Ensured shot name is not editable if the entry is linked to a Version, either through its CutItem or edit entry.
• Fixed a bug when editing shot names, and ensured linked Version is updated when needed.
• Added a "Shot name is not editable" tooltip when the shot name is not editable.
• Added a CutDiff._sg_version member, so linked Version can be edited without modifying the edit entry or the CutItem.

[raphaelmatto]

Looks great! Merge at will.