Replace all uses of replaceTexture with the new PIE4 texture tileset override directives

[past-due]

See: https://github.com/Warzone2100/warzone2100/blob/master/doc/PIE.md#texture

Describe why do you think it is needed
There is very little use of replaceTexture in the existing scripts, and it doesn't work properly in all circumstances (i.e. doesn't take into account tcmask, and normal/specular maps). Replacing with the PIE4 directives will allow us to simplify the code, resolve these issues, and drastically reduce usage of this function.