Introduce `show_single_field()` and `show_multiple_fields()`, helper methods for printing object data
Convert `wp theme get` to use new util function
Convert `wp comment get` to new util functions
Have `show_single_field()` logically persist the `--format` argument.
Run moar faster
Convert `wp user *` to new util functions.
Convert `wp site list` to new util function.
Method isn't used anymore
Convert `wp post *` to new util functions.
Remove unused methods