[algorithms.ei] cleanup
[reductors.linear] bugfix
[la.gram_schmidt] bugfix
[la.gram_schmidt] bugfix
[la.gram_schmidt] small tweak
[la.listvectorarray] bugfix
[parameters.functionals] add ExpressionParameterFunctional
[parameters] make ExpressionParameterFunctional picklable
[playground.remote] bugfix
[playground.remote] add logging to RemoteStationaryDiscretization
[playground.remote] bugfix
[parameters.base] make from_parameter_type() more flexible
[discretizations.basic] cleanup
[discretizations] add type_solution to discretization interface
[reductors] initialize RB using type_solution of discretization
[algorithms.basisextension] create empty basis of correct type
[core.interfaces] add ImmutableInterface
let every immutable class inherit from ImmutableInterface

and remove all obsolete self.lock() calls
[domaindescriptions] make DomainDescriptions and BoundaryTypes immutable
[functions.basic] bugfix