Allow fable server to run arbitrary commands
Allow fable server to run arbitrary commands

Fixes #828.

fable-compiler/Fable,ncave/Fable,fable-compiler/Fable,ncave/Fable,fable-compiler/Fable,fable-compiler/Fable,ncave/Fable,fable-compiler/Fable,fable-compiler/Fable,ncave/Fable,ncave/Fable,inosik/Fable,ncave/Fable,fable-compiler/Fable,inosik/Fable,ncave/Fable