Gridlayout

With this commit, we introduce a more general way of positioning the widgets in the plotmethod tabs that control the formatoptions. The layout of plotmethod tabs is now based on a qgridlayout with a standard interface that manages the various rows.

Furthermore, we add a combo box to select the plot type for mapplot and plot2d and changed the name for projections in the GUI to something more explanatory.

• Tests added (for all bug fixes or enhancements)
• Tests passed (for all non-documentation changes)
• Fully documented, including CHANGELOG.rst for all changes