wp-config constants worth setting on every install

A default wp-config.php leaves the file editor enabled, revisions unlimited and debugging output aimed at the browser. Four constants close most of that, and they belong in the install rather than in a plugin.

define( 'DISALLOW_FILE_EDIT', true );   // no code editing from wp-admin
define( 'WP_POST_REVISIONS', 10 );      // stop revisions filling the table
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );     // log it, never print it

The WP_DEBUG_DISPLAY pairing is the one people get backwards: with it left at the default, a notice from any plugin prints into the page and can corrupt headers or JSON responses. Logging without displaying gives the same information and no user-visible damage. WP_POST_REVISIONS is worth setting on any site with editors — an unbounded revision history is frequently the largest table in the database.