* Add rest arg to def
This commit applied adds the ability to define the rest parameter of a def
command. It does not implement the functionality to expand the rest argument in
a user defined def function.
The rest argument has to be exactly worded "...rest".
Example after this PR is applied:
file test.nu
```shell
def my_command [
...rest:int # My rest arg
] {
echo 1 2 3
}
```
```shell
> source test.nu
> my_command -h
Usage:
> my_command ...args {flags}
Parameters:
...args: My rest arg
Flags:
-h, --help: Display this help message
```
* Fix space in help on wrong side
71b99edd48