[Feature Request] Miscellaneous "fire input on" attribute requests

[therealscroob]

Rather than opening lots of individual pull requests, I thought it would be better to pool these requests into one instead.

"fire input on hurt"
fires when the user is damaged

"fire input on miss"
fires when the weapon does not hit any targets

"fire input on reflect"
fires when a pyro reflects a projectile

"fire input on medigun heal"
fires when a medigun starts healing a target

"fire input on medigun switch"
fires when a medigun stops healing a target

"fire input on reload"
fires when the weapon's loaded ammo is increased by a reload

"fire input on deploy"
fires when a weapon is switched to

"fire input on holster"
fires when a weapon is switched from