Fix weapon switching, scale, add Q key bind

- Fixed weapon switching: player.gd now uses weapon_next/weapon_prev/slot actions
  (was checking for nonexistent 'weapon_toggle')
- Added Q key to weapon_next input action
- Reduced weapon scale from 0.3 to 0.07-0.08 (was still 3x too large)

project.godot

@@ -145,6 +145,7 @@ weapon_reload={
 weapon_next={
 "deadzone": 0.5,
 "events": [Object(InputEventMouseButton,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"button_mask":0,"position":Vector2(0, 0),"global_position":Vector2(0, 0),"factor":1.0,"button_index":4,"canceled":false,"pressed":false,"double_click":false,"script":null)
+, Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":81,"key_label":0,"unicode":113,"location":0,"echo":false,"script":null)
 ]
 }
 weapon_prev={