Add a license preference field

This feature is absolutely necessary. Now a user can simply define
their default license and quickly go through a form, as opposed to
stopping to click on the select and choosing the same option over
and over again.

Also added DB migration for the field, so that's working now, too.

Rebased by Sebastian and made the default value to be unicode.

Reviewed-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

mediagoblin/db/migrations.py

@@ -184,3 +184,15 @@ def fix_CollectionItem_v0_constraint(db_conn):
         pass
 
     db_conn.commit()
+
+
+@RegisterMigration(8, MIGRATIONS)
+def add_license_preference(db):
+    metadata = MetaData(bind=db.bind)
+
+    user_table = Table('core__users', metadata, autoload=True,
+            autoload_with=db.bind)
+
+    col = Column('license_preference', Unicode, default=u'')
+    col.create(user_table)
+    db.commit()

mediagoblin/db/models.py

@@ -63,6 +63,7 @@ class User(Base, UserMixin):
     # Intented to be nullable=False, but migrations would not work for it
     # set to nullable=True implicitly.
     wants_comment_notification = Column(Boolean, default=True)
+    license_preference = Column(Unicode)
     verification_key = Column(Unicode)
     is_admin = Column(Boolean, default=False, nullable=False)
     url = Column(Unicode)