Introduce missile attribute config files.
Move missile effects configuration into missile config files.

It was previously part of weaponInfoMode_t and defined in models/weapons/*/weapon.cfg.
Missiles can now be fully defined with their config files, independently of (pseudo) weapons.
Tidy up g_missile.c and g_weapon.c.
Tidy up g_weapon.c some more.
Tidy up event handling code in cg_weapons.c.
Add alwaysImpact to bounceball and lcannon missile config files.
Merge branch 'gameplay/missile-configs' into gameplay/viech