Pipda

- Fix `have_expr`

- Functions without data arg allowed to be called independently but returns Function object

- Allow verb/function called directly with Expression objects as arguments
- Allow context passed to _context argument of function to be registered
- Add astnode_fail_warning to register_verb/func to whether warn when ast node not be able to detect
- Add verb_arg_only for register_func to restrict registered func to be just an argument of a verb
- Allow extra_contexts for specific arguments for register_verb/func
- Add debug for evaluating
- Allow inplace piping

- Allow register_verb/func to have different contexts on different types

- Add DataContext for the verbs/funcs to run with env with it.

- Revert varname configs