Add misc. custom OmegaConfg resolvers (#173)

New resolvers:
- Modulo math operator
- List indexing (using the C++ inspired name `at`)

vital/utils/config.py

@@ -34,6 +34,7 @@ def _cast_op(op, x, y, type_of: str = None) -> Any:
     OmegaConf.register_new_resolver("op.add", lambda x, y, type_of=None: _cast_op(operator.add, x, y, type_of=type_of))
     OmegaConf.register_new_resolver("op.sub", lambda x, y, type_of=None: _cast_op(operator.sub, x, y, type_of=type_of))
     OmegaConf.register_new_resolver("op.mul", lambda x, y, type_of=None: _cast_op(operator.mul, x, y, type_of=type_of))
+    OmegaConf.register_new_resolver("op.mod", lambda x, y, type_of=None: _cast_op(operator.mod, x, y, type_of=type_of))
 
     OmegaConf.register_new_resolver("builtin.len", lambda cfg: len(cfg))
     OmegaConf.register_new_resolver("builtin.range", lambda start, stop, step=1: list(range(start, stop, step)))
@@ -47,6 +48,7 @@ def _cast_op(op, x, y, type_of: str = None) -> Any:
             ]
         ),
     )
+    OmegaConf.register_new_resolver("list.at", lambda cfg, idx: cfg[idx])
 
 
 def read_ini_config(ini_config: Path) -> ConfigParser: