Database definition & tests organisation

* The main loader script has been updated to generate the list of files
it needs to load automatically. As a consequence, files that contained
manually-maintained lists of scripts have been removed, and definition
directories have been renamed accordingly.

* PostgreSQL extension loading and configuration has been moved to a
separate script to be loaded automatically in the main transaction.

* Data and function definition scripts that had the -data or -functions
suffix have been renamed (the suffix is unnecessary).

* Unit tests have been reorganised to follow the definition's structure.

* Documentation has been improved

legacyworlds-server-data/db-structure/tests/user/050-updates/105-planet-resource-regeneration/010-process-planet-res-regen-updates.sql

@@ -0,0 +1,11 @@
+/*
+ * Test privileges on sys.process_planet_res_regen_updates()
+ */
+BEGIN;
+	SELECT plan( 1 );
+
+	SELECT diag_test_name( 'sys.process_planet_res_regen_updates() - Privileges' );
+	SELECT throws_ok( 'SELECT sys.process_planet_res_regen_updates( 1 )' , 42501 );
+	
+	SELECT * FROM finish( );
+ROLLBACK;