Rename GetTexture pipeline parameters

Right now, loading a texture is done through the game module -> game engine -> renderer -> resource manager. All wrapping methods still have the parameter as "filepath" which is misleading since the parameter can be any name and not just a file path.

Since we can register an asset to a friendly name such as "jump" being associated to "assets/animations/jump_anim.png" it would be handy to rename the parameter to something like "assetName" or something.