Prepared to support exchange format version 0.9.1

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Allow to upload model solution files

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Reuse input stream to output stream copy method

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Export files and model-solutions

Signed-off-by: Sven Strickroth <email@cs-ware.de>