[Unity] Remove specific warnings

Create csc.rsp into Asset folder and write these lines to remove warnings
-nowarn:0414
-nowarn:0219
-nowarn:0649
-nowarn:0168

Meaning:
warning CS0414: The private field `___' is assigned but its value is never used
warning CS0219: The variable `___' is assigned but its value is never used
warning CS0649: "Field is never assigned"
warning CS0168: The variable `___' is declared but never used