Müller, Felix authored Mar 12, 2020 and Praetorius, Simon committed Jul 11, 2020

Remove BiLinearForm::pattern_
Change Pattern to be created in BiLinearForm::init()
Change BiLinearForm Observer to set a flag instead of directly rebuilding the pattern
Change Pattern ctor to replace call to init
Make Pattern::init protected
Add MatrixFacade::init() and implementations MatrixBackend::init() with no argument
Change MTL matrix backend slot size calculation