[Freeciv-Dev] (PR#4426) Adding append command to gui-gtk-2.0

["Vasco Alexandre da Silva Costa" <vasc@xxxxxxxxxxxxxx>]

I like the idea, but I will not apply any wide changes to the worklist
code in the client until the common worklist code stops being braindead.

i.e. it makes no sense current production is a separate struct field.
The current production should simply be the first element in the
worklist queue.

Regarding worklist manipulating commands for the city report, I propose
the following names and commands:

* prepend (add to the beggining of the worklist).
* append (add to the end of the worklist).
* pop first.
* pop last.

These could be submenus of the "Change" menu in the city report. Thus:

Change
 +- Prepend to Worklist
 |  +- Units
 |  +- Improvements
 |  +- Wonders
 |
 +- Append to Worklist
 |  +- Units
 |  +- Improvements
 |  +- Wonders
 |
 +- Pop First in Worklist
 +- Pop Last in Worklist
 +- CMA