Half-Life FGD files

Improved Half-Life and Half-Life: Opposing Force FGD files for JACK level editor.

Warning: it was never tested with other level editors!

Based on .fgd files that bundled with JACK.

Changelog

• Add Animation sequence field with full list of animations for all monster entities.
• Set the default animation sequence to some kind of idle for all monster entities.
• Add studio model for monster_hevsuit_dead.
• Add studio() property for monster_generic and monster_furniture in halflife-op4.fgd to enable view of custom model.
• Change class for some dead monster entities in halflife-op4.fgd to match entity color of other dead bodies.