Site properties

We needed the feature to set configuration on different sites. This PR gives you the ability to specify site specific configuration options in a YAML file. This file is then read by a generator that creates rows in a site_properties table. The properties is also created when you create a new site. The properties are then changed under a "site properties" view, available by clicking the property icon in the site list.

Notable things that are not implemented is changes in the yml file other than adds. If you change the name of a property there are no feature for changing the names in the DB. Same goes for deleting properties from the yml file.