CLI command to migrate users to profiles

[mboynes]

WP-CLI command would find all users with posts, check if there's already a Profile (check both by relationship [#3] and email), and if not, create a new Profile and copy the data over.

[renatonascalves]

Note: make it easier to move user-related meta into their equivalent in the profile post type. Or saying it in another way, it needs to be flexible enough for each site. Otherwise, a custom CLI command might be preferable.

[renatonascalves]

Just a note that this package introduced support to map users too.