Mounts should be able to affect weapons' reload rate

**What do you want to see?**
There should be a reload time percentage option on mounts. Adjusting this would affect a weapon's reload rate, so 50 would make it fire twice as often and 200 would make it fire half as often.

**How would it help players?**
More tactical options for modders and players. A heavy mount could be adjusted to do even more damage, but fire less often, to make it even more distinct from a regular weapon. Or you could create a true gatling mount that sprays shots everywhere instead of just being a tiny version of a normal weapon that you have to spam on your designs!

**Alternatives**
Could be a ratio (e.g. x2) or a flat modifier (e.g. +2 turns) but a percentage sounds the most balanced and consistent with existing mount options.

**Screenshots and mockups**
N/A

**Things to consider**
???

**Related issues**
This option would mesh well with salvo size options (#501).