Bert RPC access and argument conversion
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Bert manage MFA access list.

{accept, Mod}
{accept, Mod, Func, Arity}

{reject, Mod}
{reject, Mod, Func, Arity}

{redirect, [ {M, M'} | {{M,F,A},{M',F',A'}} ]}

Mod == {accept, Mod}
{M,F,A} == {accept,M,F,A}

{propargs,Mod,Func,ArgSpec} 
  ArgSpec = keep | [Arg | ArgSpec]

  Arg = Name::atom() 
      | {args,ArgSpec}  -- get nested arguments
      | {opt,Name::atom(),Default::term()}
      | {Convert, Name::atom()}
      | {Convert, Name::atom(), Default::term()}

  Convert = string_to_integer |
       | string_to_float |
       | string_to_atom