[sql] ajout de la colonne pad_url, modification de la colonne content pour accepter NULL

TODO: Appliquer le patch sql/patches/mysql/01-pad_url.sql sur les db
existantes

sql/mysql.sql

 	lang varchar(16) not null,
 	slug varchar(128) not null,
 	title varchar(256) not null,
-	content text not null,
+	content text null,
 	sidebar text not null,
 	users_only integer not null,
-	constraint unique (lang,slug)
+	constraint unique (lang,slug),
+	pad_url varchar(256) null
 ) Engine = InnoDB;
 
 create table history (
 	created datetime not null,
 	author varchar(32) not null,
 	title varchar(256) not null,
-	content text not null,
+	content text null,
 	sidebar text not null,
 	constraint unique(id,version),
+	pad_url varchar(256) null,
 	foreign key(id) references pages(id),
 	primary key(id,version)
 ) Engine = InnoDB;

sql/patches/mysql/01-pad_url.sql

+alter table pages
+add column pad_url varchar(256) null;
+alter table pages
+modify column content text null;
+
+alter table history
+add column pad_url varchar(256) null;
+alter table history
+modify column content text null;