remove template arguments from ThisType to save refactoring work

dune/xt/common/parameter.hh

dune/xt/functions/ESV2007.hh

dune/xt/functions/base/combined-functions.hh

dune/xt/functions/base/combined-grid-functions.hh

dune/xt/functions/base/composition.hh

dune/xt/functions/base/function-as-grid-function.hh

dune/xt/functions/base/reinterpret.hh

dune/xt/functions/checkerboard.hh

dune/xt/functions/constant.hh

dune/xt/functions/expression/base.hh

dune/xt/functions/expression/default.hh

dune/xt/functions/flattop.hh

dune/xt/functions/grid-function.hh

dune/xt/functions/indicator.hh

dune/xt/functions/interfaces/element-functions.hh

dune/xt/functions/interfaces/function.hh

dune/xt/functions/interfaces/grid-function.hh

dune/xt/functions/spe10/model1.hh

dune/xt/functions/spe10/model2.hh

dune/xt/grid/bound-object.hh