[Feature] Autocomplete argument and option names in commands

[stof]

It would be great to autocomplete argument and option names in $input->getArgument('...') and $input->getOption('...') inside columns, by reading the command definition to know them.

[stof]

2 things to check for your implementation (I cannot tell whether it is supported just by reading the code):

• does setDefinition() properly reset arguments/options which might have been added earlier ?
• does it work with inheritance when the parent code configuring some options and arguments gets called ?

[Haehnchen]

• setDefinition() reset: its too complex code interpreting for this simple completion context
  • good catch on inheritance, used in some symfoy2 core commands

[Haehnchen]

parent implemented