Function prefix conflict with PMPro User Pages

[dparker1005]

Both PMPro Unlock Protocol and PMPro User Pages use the function prefix pmproup_. Since this plugin is newer and likely has fewer installs and fewer custom setups built off of it, this plugin should be updated to use a new function prefix.

Ideally, we can also support the old function/filter names as long as they don't conflict with PMPro User Pages. Maybe we can declare them on init if the function name is not already taken in a deprecated.php file.