Check length of compositions, output type

I think at 0.4 us/call on this machine

needed a force eval, () needed to be moved

Method from Ulrich Deiters, superancillary from our new paper

added CMakeSettings.json for working with VisualStudio
added missing "template" to dependent template-function calls

Co-authored-by: Tobias Loew <tobi@die-loew.de>

And JSON I/O

Also add the accessors as methods of the class in the python interface (overload resolution has large runtime overhead)

See #2

See #2

See #2