The `Editor` is very useful for correctly opening a text editor and making changes
to some initial input. The current use of `Editor` is only for getting input for
commets.
However, it would also be useful for opening up a text editor on some other
existing files or text, for example, in the command `rad config edit`.
The `Editor` struct was changed to have two new options, `truncate` and
`cleanup`, to allow the user of the struct to dictate whether existing text is
truncated, and if the underlying file should be remove.
The original `new` method is now named `comment`, mimicing the existing
construction of a temporary `RAD_COMMENT` file.
The new version of `new` accepts any file for the `Editor` and will open it
without truncating or removing the file.
`Editor` is now used for the `rad config edit` command.
Adds `set`, `add`, `remove`, `delete` to `rad config`.
Note that the changes will affect the configuration file, but not the
running instances. For changes to be reflected in the running instances
the node would need to be restarted.
Fintan Halpenny
Johannes Kuehlewindt
cloudhead