Deprecated several functions related to submissions.
Changed the method name of Ninja_Forms()->subs()->get_subs() to just Ninja_Forms()->subs()->get().
Added a filter for the pre and postfix submission sequential ID.
Fixed a bug where editing a submission caused the "back to list" button to not work.
Changed the method name of Ninja_Forms()->subs()->get_subs() to just Ninja_Forms()->subs()->get().
Added a sort code for the sequential submission ID.
Removed the options for pre and postfix sequential submission ID.
Changed the "insert_sub" and "update_sub" action hooks to the new nf_save_sub action hook.