[common.configuration] add comparison operators, also for ParameterTree
[common.float_cmp] add float_cmp() as in pyMOR

This implementation for float_cmp works better for me in a lot if places.
We should use it in the other implementation in the long run...
[functions.global] add name() and type() to GlobalLambdaFunction
[la.container.matrix-interface] whitespace
[functions.interfaces] add name() and type() to GlobalFunctionInterface
[functions.interfaces] whitespace
[functions.expression] add sanity check to evaluate()