reporting: simplify code (remove sections object)

matlab/reports/@page/addSection.m

matlab/reports/@page/numSections.m

matlab/reports/@page/page.m

matlab/reports/@page/write.m

matlab/reports/@report/addGraph.m

matlab/reports/@report/addSeries.m

matlab/reports/@report/addTable.m

matlab/reports/@report/addVspace.m

matlab/reports/@section/subsasgn.m

matlab/reports/@sections/addSection.m

matlab/reports/@sections/display.m

matlab/reports/@sections/end.m

matlab/reports/@sections/getSections.m

matlab/reports/@sections/numSections.m

matlab/reports/@sections/sections.m

matlab/reports/@sections/subsasgn.m

matlab/reports/@sections/subsref.m

matlab/reports/@sections/write.m