Custom Shapes and Reference Lines Party

• updated vignettes and examples
• added citation and start up message
• added major_x_labels argument for custom x labels
• added interval_linewidth argument to control interval linewidth
• added and exported the expand_modelframe function
• added the possibility to select the shapes manually via interval_shape and bsv_shape
• added capability for the user to reverse color legend separately via legend_color_reverse
• added capability for the user to specify text for legend titles via interval_legend_title and shape_legend_title as well as to control legend title text size via legend_title_size
• added capability for the user to specify facet text color via x_facet_text_col and y_facet_text_col for improved theming support
• added possibility to add different ref line(s)/area(s) by parameter via ref_value_by_panel and ref_value_by_panel_data function arguments (not in the shiny, app)