Add stretching of modules and modules-center toggling

This Patch allows the stretching of modules-{left,center,right} as well
add a "expand" flag to AModule. This allows one module to consume the
leftover space.
To allow the left or right modules to fully consume the center, the
changes also include a way to remove the center box (center_)
altogether.

man/waybar.5.scd.in

@@ -23,6 +23,21 @@ The visual display elements for waybar use a CSS stylesheet, see *waybar-styles(
 
 # BAR CONFIGURATION
 
+*expand-center* ++
+	typeof: bool ++
+	default: false ++
+	Enables the modules-center to consume all left over space dynamically.
+
+*expand-left* ++
+	typeof: bool ++
+	default: false ++
+	Enables the modules-left to consume all left over space dynamically.
+
+*expand-right* ++
+	typeof: bool ++
+	default: false ++
+	Enables the modules-left to consume all left over space dynamically.
+
 *layer* ++
 	typeof: string ++
 	default: bottom ++
@@ -68,6 +83,11 @@ The visual display elements for waybar use a CSS stylesheet, see *waybar-styles(
 	typeof: integer ++
 	Margins value without units.
 
+*no-center* ++
+	typeof: bool ++
+	default: false ++
+	Option to disable the center modules fully usefull together with expand-\*.
+
 *spacing* ++
 	typeof: integer ++
 	Size of gaps in between the different modules.