public void changeData(final boolean clear, final Action1<Action3<Integer, Integer, Boolean>> changeAction) {
        final Action1<Action3<Integer, Integer, Boolean>> realChangeAction = clear ?
                changer -> {
                    executeFor(-1, -1, (r, c) -> changer.call(r, c, false));
                    changeAction.call(changer);
                } :
              changeAction;
        changeDataInternal(realChangeAction);
    }
Change data of the matrix. if clear=true, then matrix will be cleared before change is executed.
Use the given changeAction to execute changes. Call it with parameters (row, column, check)
to set field in a row/column to value "check"
main/src/main/java/cgeo/geocaching/ui/CheckboxMatrixView.java