exception handling during sync

added 21 commits

• 3db8ef80...8d5d83d0 - 18 commits from branch develop
• 3b0e7e85 - ctrl+c breaks sync correctly
• 09cdb996 - exception during sync stops the sync process gentle
• 85a1b770 - support SIGTERM during sync

Compare with previous version

added 5 commits

• 85a1b770...73075dc0 - 2 commits from branch develop
• 3c8077cd - ctrl+c breaks sync correctly
• 29322aee - exception during sync stops the sync process gentle
• 07adac5a - support SIGTERM during sync

Compare with previous version

added 7 commits

• 07adac5a...beda6b94 - 4 commits from branch develop
• 8730d584 - ctrl+c breaks sync correctly
• 045603f1 - exception during sync stops the sync process gentle
• 7940ea1b - support SIGTERM during sync

Compare with previous version

merged

mentioned in commit d90efed9