Feature/redactor autosave

Fixes #149 and integrates autosave based on time with the following details:

- 3 seconds after the last change the content will be saved. 
- On escape button or when leaving the editor the content, from the moment the editor was opened, will be restored and the editor will be closed. 
- The save button only fires another save, if not all changes where already saved and closes the editor. 
- The infopark save api is used, so that the normal behaviour like a warning on page leave with pending changes, are still in use

To give the user a consistent interface autosave should also be integrated in string content fields ( #151 ).