wip for db_migrations for core schema

sql/pgsql/migrations/26.sql

@@ -0,0 +1,13 @@
+insert into ttrss_prefs (pref_name,type_id,def_value,short_desc,section_id) values('PURGE_UNREAD_ARTICLES', 1, 'true', 'Purge unread articles',3);
+
+alter table ttrss_users add column created timestamp;
+alter table ttrss_users alter column created set default null;
+
+create table ttrss_enclosures (id serial not null primary key,
+	content_url text not null,
+	content_type varchar(250) not null,
+	title text not null,
+	duration text not null,
+	post_id integer references ttrss_entries(id) ON DELETE cascade NOT NULL);
+
+update ttrss_version set schema_version = 26;