Enclose edit/new records table in form method=post

Posts-insert form with method=post ensures correct submitting
of edit and new records.

* In FCT_Records_List_Table::display_tablenav method #posts-insert form included
* Rename pre/post posts form hook
* Tidy up FCT_Records_List_Table code
* Added current_user_can() checks to fct_adminis_{edit|new|view}_records()