Save/load production queues

[Oberlus]

Feature request

Idea

(Adapted from #884)

• Add methods for players to define, save and load production queue recipes.
• Add a config option for a single recipe loaded on game start, defaulted to a pre-defined recipe.

A recipe would be an ordered list of ships and buldings that are added to the players production queue once loaded, possibly with an individual limit in size.
Recipe is a loose term, used here only to assist with description.

Discussion

Forum:
https://www.freeorion.org/forum/viewtopic.php?f=2&t=11931 (old, also asking for research queue recipes)
https://freeorion.org/forum/viewtopic.php?f=28&t=12258 (latest)