Remove "adventure layer" from IObject

[ghost]

This PR strips "adventure layer" from the default IObject type in the engine. This "layer" is actually represented only by IHotspotComponent that contains interaction setup (reaction to player commands). The idea is to have IObject as a base class for something that has visuals, but not necessary associates with adventure genre (interaction schemes). The adventure-specific class could be added later (based on Object and having HotspotComponent, and maybe other things).

Besides removing IHotspotComponent from IObject, I had to do following changes:

• Replace Hotspot string property with DisplayName property, added to IEntity. This makes it possible to assign human-readable name or description to any entity in game.
• In exchange, add DisplayHotspot boolean property to IHotspotComponent, which lets to enable or disable showing hotspot's name under mouse cursor.

[ghost]

I just realized that although I removed IHotspotComponent inheritance from the IObject interface, I did not remove it from implementation.

[tzachshabtay]

Right, that needs to be fixed.

[ghost]

Updated.

Oh, had to rebase.

[tzachshabtay]

Looks good, though I think you missed the comment about adding the "seealso" tag.

[ghost]

But I added it. Or there's something else needed here? Maybe github shows cached commit contents?

[tzachshabtay]

Oh, sorry, I see it now. Ok, merging.