remove spingfox for ApiIgnore direction
use swagger-maven-plugin to generate swagger.json before compiling rather than
 dynamically generate it on request

Removed unused schemas and updated the remaining for Spring 4.1.

At least caching of learning progress responses
did not work since commit a59eb75f on March, 6th.

While the exact origin of this problem is unclear,
it seemed like Spring was creating more than one
databaseDao bean. One of these beans had no
working caching annotations.

The context:property-placeholder config element does not work as
intended. See https://jira.spring.io/browse/SPR-9989.

Having content negotiation with more than just JSON content
might follow REST principles.

All entities annotated with e.g. @XmlRootElement can be send as XML data.
This requires client to send Accept header with value "application/json"
to fetch JSON responses.
Default Accept header send by client is something like:
"text/html,application/xhtml+xml,application/xml"
which requests an XML document, not JSON document but JSON is expected.

This should enable annotation based cache-control header values.
Added a cache max age of 60 seconds to statistics resource. Proxy-Servers
should cache a statistics resource for about 60 seconds.

This will allow dynamic configuration depending on property file settings.

Removed connector client bean from XML based configuration and added bean
creation into JavaBased config class. Bean will be created if there is
a property "connector.enable" with value "true" otherwise no bean will
be created wich has the same behavior removing bean definition from XML
configuration file.

No need to change application config - can be done in property file :-)

Permission handling is the same as with removed Authorized annotation