Added docket_multipage.xsl as a copy of docket.xsl
Merge pull request #175 from frank-ulrich-weber/docket_multipage

Added docket_multipage.xsl as a copy of docket.xsl
Refactor LongRunningTask
Remove useless TiffWriterTask
Create a better task manager
Use new task manager in task form
Implement methods of TaskManager
Remove duplicate entry for org.goobi.production.ImageIOInitializer
Add javadoc
Create shutdown listener
Write Housekeeper
Some refactoring
Add description to configuration
Update configuration
Improving the front end
More development, documentation etc.
Calculate button appearance depending on thread state, not progress bar
Use API to copy file (more efficient)
Write ExportDmsTask
First working version