Adds sounds to falling over

Resting and buckling are still silent.
Merge pull request #2501 from Tenebrosity/fallsounds

Adds sounds to falling over
- Removes the throwtapsound var from items. It was unnecessary.

- Thrown items play throwhitsound on impact. If no throwhitsound is defined, they play hitsound instead. If that isn't defined, they play genhit.ogg. The latter fixes \#2508. The volume of the sound is dependant on the item's throwforce and/or weight class.

- Adds 15 throwforce to the fireaxe, which previously had only 1.