ET: add property to shots

[jblom]

CERTH technology has a way of indicating the key/unique shots (within a scene).

e.g. in an interview scene, there can be many similar shots that show the interviewer and the interviewee. CERTH has an algorithm for marking unique shots.

(this information is useful for presenting the different shots in a video)

The proposal is to add a property to shots, such as:

• linkedtv:IsUniqueShot
• linkedtv:IsMainShot

(please come up with a better name ;) )