Improve website configuration and use property-placeholders

- Change datasource.properties to webservices.properties
  and add cors.allow-origins to it
- Add website.properties to the website module and add
  cors.allow-credentials and cors.allow-origins to it
- Add property-placeholder for webservices.properties
- Add CORS headers using a HandlerInterceptorAdapter and
  use the property-placeholder to interpolate the headers
- Replace ContentController with <mvc:view-controller />
- Remove applicationContext.xml and the corresponding
  ContextLoaderListener in the website module
- Add load-on-startup for DispatcherServlet in web.xml
- Add <mvc:default-servlet-handler/> to spring-servlet.xml
- Set "/" a the only url-pattern in web.xml
Use dateTime instead of date for the created attribute

- Use data-type xsd:dateTime instead of xsd:date on
  the created attribute in content.xsd
- Use 'medium' instead of 'mediumDate' to format
  the value in index.jsp
Client-side improvements (and a bugfix)

- Add missing call to content.remove() that was accidentally
  dropped in 3fd5396ceec826a641fca8b3257cb9ab318dc237
- Avoid reading from $scope in ContentController by
  passing the appropriate parameters to add and edit
- Rename ContentController to ContentCtrl
- Wrap the new content message in a <p/>
- Add CSS to grey the div and center the text
- Change spaces to tabs in $.ajax() call
- Use the Google+ displayName as the author's name
  (with no option to set it), making it possible to
- Remove the authorForm and associated CSS