[linearelliptic.discretizations.block-swipdg] clean up dead code
[linearelliptic...block-swipdg] mark solve_for_local_correction() untrusted
[linearelliptic...block-swipdg] add get_local_discretization()
[linearelliptic...block-swipdg] add oversampled discretizations
[linearelliptic.problems.default] add ConvertToDefault
[gitignore] add .pyc
[linearelliptic.estimators.block-swipdg] update local indicators
[linearelliptic.testcases...] add H_with_h (default to false)

This allows to run a multiscale test case where coarse and fine grid are
refined, such that H/h is constant.
[...estimators.swipdg] use over_integrate more often
[...estimators.block-swipdg] use over_integrate more often
[test...] fix typo
[test...block-swipdg-expectations] update rates
[test...block-swipdg-expectations...] drop mu_minimizing