Merge branch 'issue/periodic_bc' into 'master'
Periodic BC implemented by Siqi Ling added to this branch Rewritten periodic BC, to be compatible in sequential and parallel and to allow mixed finite element spaces. See merge request !9
Periodic BC implemented by Siqi Ling added to this branch Rewritten periodic BC, to be compatible in sequential and parallel and to allow mixed finite element spaces. See merge request !9