[core.logger] fix minor typos
[operators.cg] add support for Neumann boundaries in L2ProductFunctionalP1, L2ProductFunctionalQ1
[domaindescriptions] add more assertions
[la] add assertion to generic lgmres solver
[domaindescriptions] fix boundary type assertions
[packaging] remove install.py

Script is unmaintained and not used by anyone ..
also removes install.py from setup.py
[grids] minor fix in Triangle.quadrature
[grids] allow periodic boundaries for TriaGrid
[operators] fix L2ProductFunctionalP1 for order 1 in 1D
[operators] add lincomb method
[discretizations] allow to specify additional functionals
[operators] deprecate OperatorInterface.lincomb
[operators] move LincombOperator to pymor.operators.constructions
code cleanup
always use fully qualified imports
[tests] fix discretization fixtures

We now have TriaGrid as default, so diameters need to be adapted.
[operators.cg] Add support for matrix-valued diffusion functions
[tests] remove Unpicklable mixin
[analyticalproblems] allow to specify a parameter space for EllipticProblem