v2.0 backend refactor

Created by: brantje

• Add checks (if item exist, if item not expired,etc)
• Add public api so apps can be made
• Update the $this->params is deprecated (see here: http://doc.owncloud.org/server/7.0/developer_manual/app/controllers.html#getting-request-parameters )
• Other stuff i forgot
• Convert current routes to restful api routes (http://doc.owncloud.org/server/7.0/developer_manual/app/api.html)

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