This addition requires a number of changes including:
- the addition of a new `_join` function
- reformatting of the `add` function to facilitate the longer lines
These commands make it possible to disable records without fully
removing them. To 'disable' a record, it simply is commented out with
the following pattern `#disabled: ` prepended to the line.
Displaying a record pair for a hostname or IP address is likely a common
operation, and using the `show` name makes it clear what the primary
function of the command is. Since record pairs are very simple, the
easiest way to allow both hostname and ip address arguments is to use
grep, which also provides general search-like functionality. In order to
avoid doubling this functionality, use the `show` command in the `list`
command for search.
