[Gameplay A24] - Drastically change artillery attacks.

Artillery is not that effective in 0 A.D., partly because their damage per second is unimpressive (especially compared to rams or war elephants), partly because of their splash damage.
Splash damage was added in r11886 / rP11886 (nearly eight years ago). The values have changed multiple times, as has the exact calculation (see simulation/components/Attack.js). While it's quite interesting in theory, in practice it's not that effective. @fatherbushido explained how it works on the forums. It's important to understand the actual splash damage depends on the distance to the centre of entities, in contrast to ordinary attacks, which do full damage when they hit the footprint (edge).
Splash damage has some serious problems:

• It may have no effect vs entities with footprints longer than the splash radius, such as many (most?) structures and warships.
• The AI does not take it into account.
• It's anachronistic: exploding shells did not exist yet in 0 A.D.'s timeframe. Missiles were rigid objections, and even the very largest projectiles were well under a metre in diameter.

This patch therefore removes splash damage from artillery (except bolt shooters).
Fireships and fireraisers now deal fire damage instead of a combination of other damage types.

Basically, stone throwers are good against large unit masses and structures only, while bolt shooters are unit killers.
Artillery and bolt towers no longer get additional projectiles from garrisoned units.
Roman artillery does not get a larger range but keeps the increased damage.

Patch by: @Nescio
Differential revision: D2494
Reviewed by: @borg-, @wraitii
Comments by: @Angen, @Stan