Mesh shields (#2013)

# Description
This PR is based on the request raised in #2013 and uses the shield mesh supplied by @lionhearted adapted for the Wave as the Lanner has been removed.

This simply fades a mesh based shield in/out based on what percentage of it is left so it's a direct replacement for the existing effect. I'm too wiped out to do hit effects and things at the moment.

# Issues
There's some funky code I'm not happy with in Shield::Render where it acquires the shield material and sets the specialParameter0 so it can pass the shieldStrength through.

Also the idea of it being in with the other meshes feels a bit hacky so alternative suggestions are welcome.

Thanks,

Andy