`xcvradm` could use parseable output

Many illumos tools support a parseable mode, in which the output is regularly-structured and meant for machine consumption. Rather than nicely-printed tables, output is formatted with a single, often configurable, separator character. xcvradm could benefit from such a mode. Flags to implement include:

• -p or --parseable: select parseable mode, over human-friendly formatting
• -s or --separator: select the separator character
• -o or similar: the list of fields to include in the output. It's also nice to print a list of the available fields, in lieu of a man page.
• -H or --no-header: do not print headers for the selected columns